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Solve: 2 a 2 = 6 a + 18 .

a = −5

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Solve: 4 k 1 = 7 k + 17 .

k = −6

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In the last example, we could have made the left side the “variable” side, but it would have led to a negative coefficient on the variable term. (Try it!) While we could work with the negative, there is less chance of errors when working with positives. The strategy outlined above helps avoid the negatives!

To solve an equation with fractions, we just follow the steps of our strategy to get the solution!

Solve: 5 4 x + 6 = 1 4 x 2 .

Solution

Since 5 4 > 1 4 , make the left side the “variable” side and the right side the “constant” side.

.
Subtract 1 4 x from both sides. .
Combine like terms. .
Subtract 6 from both sides. .
Simplify. .
Check: 5 4 x + 6 = 1 4 x 2 Let x = −8 . 5 4 ( −8 ) + 6 = ? 1 4 ( −8 ) 2 −10 + 6 = ? −2 2 −4 = −4
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Solve: 7 8 x 12 = 1 8 x 2 .

x = 10

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Solve: 7 6 y + 11 = 1 6 y + 8 .

y = −3

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We will use the same strategy to find the solution for an equation with decimals.

Solve: 7.8 x + 4 = 5.4 x 8 .

Solution

Since 7.8 > 5.4 , make the left side the “variable” side and the right side the “constant” side.

.
Subtract 5.4 x from both sides. .
Combine like terms. .
Subtract 4 from both sides. .
Simplify. .
Use the Division Propery of Equality. .
Simplify. .
Check: .
Let x = −5 . .
.
.
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Solve: 2.8 x + 12 = −1.4 x 9 .

x = −5

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Solve: 3.6 y + 8 = 1.2 y 4 .

y = −5

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Key concepts

  • Beginning Strategy for Solving an Equation with Variables and Constants on Both Sides of the Equation
    1. Choose which side will be the “variable” side—the other side will be the “constant” side.
    2. Collect the variable terms to the “variable” side of the equation, using the Addition or Subtraction Property of Equality.
    3. Collect all the constants to the other side of the equation, using the Addition or Subtraction Property of Equality.
    4. Make the coefficient of the variable equal 1, using the Multiplication or Division Property of Equality.
    5. Check the solution by substituting it into the original equation.

Practice makes perfect

Solve Equations with Constants on Both Sides

In the following exercises, solve the following equations with constants on both sides.

3 m + 9 = −15

m = −8

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−77 = 9 b 5

b = −8

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60 = −21 x 24

x = −4

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−14 q 2 = 16

q = 9 7

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Solve Equations with Variables on Both Sides

In the following exercises, solve the following equations with variables on both sides.

21 k = 20 k 11

k = −11

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b = −4 b 15

b = −3

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4 x + 3 4 = 3 x

x = 3 4

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−11 r 8 = −7 r

r = −2

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Solve Equations with Variables and Constants on Both Sides

In the following exercises, solve the following equations with variables and constants on both sides.

6 x 17 = 5 x + 2

x = 19

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21 + 18 f = 19 f + 14

f = 7

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12 q 5 = 9 q 20

q = −5

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8 c + 7 = −3 c 37

c = −4

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5 y 30 = −5 y + 30

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7 x 17 = −8 x + 13

x = 2

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9 p + 14 = 6 + 4 p

p = 8 5

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3 y 4 = 12 y

y = 4

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5 3 c 3 = 2 3 c 16

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7 4 m 7 = 3 4 m 13

m = −6

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11 1 5 a = 4 5 a + 4

a = 7

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5 4 a + 15 = 3 4 a 5

a = −40

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3 5 p + 2 = 4 5 p 1

p = 15

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14 n + 8.25 = 9 n + 19.60

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13 z + 6.45 = 8 z + 23.75

z = 3.46

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2.4 w 100 = 0.8 w + 28

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2.7 w 80 = 1.2 w + 10

w = 60

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5.6 r + 13.1 = 3.5 r + 57.2

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6.6 x 18.9 = 3.4 x + 54.7

x = 23

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Everyday math

Concert tickets At a school concert the total value of tickets sold was $1506. Student tickets sold for $6 and adult tickets sold for $9. The number of adult tickets sold was 5 less than 3 times the number of student tickets. Find the number of student tickets sold, s , by solving the equation 6 s + 27 s 45 = 1506 .

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Making a fence Jovani has 150 feet of fencing to make a rectangular garden in his backyard. He wants the length to be 15 feet more than the width. Find the width, w , by solving the equation 150 = 2 w + 30 + 2 w .

30 feet

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Writing exercises

Solve the equation 6 5 y 8 = 1 5 y + 7 explaining all the steps of your solution as in the examples in this section.

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Solve the equation 10 x + 14 = −2 x + 38 explaining all the steps of your solution as in the examples in this section.

x = 2 Justifications will vary.

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When solving an equation with variables on both sides, why is it usually better to choose the side with the larger coefficient of x to be the “variable” side?

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Is x = −2 a solution to the equation 5 2 x = −4 x + 1 ? How do you know?

Yes. Justifications will vary.

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Self check

After completing the exercises, use this checklist to evaluate your mastery of the objectives of this section.

This is a table that has four rows and four columns. In the first row, which is a header row, the cells read from left to right: “I can...,” “Confidently,” “With some help,” and “No-I don’t get it!” The first column below “I can...” reads: “solve an equation with constants on both sides,” “solve an equation with variables on both sides,” and “solve an equation with variables and constants on both sides. ” The rest of the cells are blank.

What does this checklist tell you about your mastery of this section? What steps will you take to improve?

Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
Aislinn Reply
cm
tijani
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John Reply
what is physics
Siyaka Reply
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Jude Reply
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
David Reply
what is viscosity?
David
what is inorganic
emma Reply
what is chemistry
Youesf Reply
what is inorganic
emma
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
Krampah Reply
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
Sahid Reply
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
Samuel Reply
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Joseph Reply
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
Ryan
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Maurice Reply
what are the types of wave
Maurice
answer
Magreth
progressive wave
Magreth
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Muhammad Reply
fine, how about you?
Mohammed
hi
Mujahid
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
yasuo Reply
Who can show me the full solution in this problem?
Reofrir Reply
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Source:  OpenStax, Elementary algebra. OpenStax CNX. Jan 18, 2017 Download for free at http://cnx.org/content/col12116/1.2
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