1. To solve an equation with variables on both sides, use inverse operations to "collect" variable terms on one side of the equation.
Helpful Hint
Equations are often easier to solve when the variable has a positive coefficient. Keep this in mind when deciding on which side to "collect" variable terms.

2. Move variable to one side
Steps
Move variable to one side
Add/subtract
Multiply/divide

3. Solving Equations with Variables on Both Sides
Solve 7n – 2 = 5n + 6.
7n – 2 = 5n + 6
1: Move variable to one side
–5n –5n
2n – 2 =
2: Add/subtract
3: multiple/divide
2n =
n = 4

4.  Solve the equation. Check your answer. 4b + 2 = 3b 4b + 2 = 3b
1: Move variable to one side
–3b –3b
2: add/subtract
b + 2 = 0
Check
4b + 2 = 3b
– 2 – 2
b = –2
4(–2) (–2)
– –6 
–6 –6

5. Solve the equation. Check your answer.
y = 0.7y – 0.3
1: Move variable to one side
y = 0.7y – 0.3
–0.3y –0.3y
2: add/subtract
= 0.4y – 0.3
3: Multiple/divide
= 0.4y
Check
y = 0.7y – 0.3
(2) (2) – 0.3
2 = y
– 0.3 

6. Now you try 4a – 3 = 2a + 7 -3r + 9 = -4r + 5 3d + 8 = 2d – 17
2x – 7 = 5x – 10
a = 5
r = -4
d = -25
x = 1

7. To solve more complicated equations, you may need to first simplify by using the Distributive Property or combining like terms.

8. Don’t call me after midnight
1. D= Distributive property
2. C= combine like term
3. M = move variable to one side
4. A = addition/subtraction
5. M = Multiplication/division

9. Solve the equation. Check your answer.
3x + 15 – 9 = 2(x + 2)
D: distributive Property
3x + 15 – 9 = 2(x + 2)
3x + 15 – 9 = 2(x) + 2(2)
3x + 15 – 9 = 2x + 4
C: Combine like term
3x + 6 = 2x + 4
M: move variable to one
side
–2x –2x
x + 6 =
– – 6
A: add/subtract
x = –2

10. Simplifying Each Side Before Solving Equations
4 – 6a + 4a = –1 – 5(7 – 2a)
D: Distributive P.
4 – 6a + 4a = –1 –5(7 – 2a)
4 – 6a + 4a = –1 –5(7) –5(–2a)
4 – 6a + 4a = –1 – a
C: Combine like terms
4 – 2a = – a
M: move variable to
One side
+2a a
= a

11. = a
= 12a
A: add/subtract
M: multiply/divide

12. Solve the equation. Check your answer.
D: Distributive Property
M: Move variable to one side
3 = b – 1
A: Add/subtract
4 = b

13. Check 
5 5

14.  3x + 15 – 9 = 2(x + 2) Check 3(–2) + 15 – 9 2(–2 + 2)
3(–2) + 15 – (–2 + 2)
– – (0)
0 0 

15. Additional Example: Application
Jon and Sara are planting tulip bulbs. Jon has planted 60 bulbs and is planting at a rate of 44 bulbs per hour. Sara has planted 96 bulbs and is planting at a rate of 32 bulbs per hour. In how many hours will Jon and Sara have planted the same number of bulbs? How many bulbs will that be?
Person
Bulbs
Jon
60 bulbs plus 44 bulbs per hour
Sara
96 bulbs plus 32 bulbs per hour

16. Additional Example Continued
Let h represent hours, and write expressions for the number of bulbs planted.
60 bulbs
plus
44 bulbs each hour
the same as
96 bulbs
32 bulbs each hour
When is ?
h = h
h = h
To collect the variable terms on one side, subtract 32h from both sides.
–32h –32h
h = 96

17. Additional Example Continued
h = 96
Since 60 is added to 12h, subtract 60 from both sides.
– – 60
12h = 36
Since h is multiplied by 12, divide both sides by 12 to undo the multiplication.
h = 3

18. Additional Example Continued
After 3 hours, Jon and Sara will have planted the same number of bulbs. To find how many bulbs they will have planted in 3 hours, evaluate either expression for h = 3:
h = (3) = = 192
h = (3) = = 192
After 3 hours, Jon and Sara will each have planted 192 bulbs.

19. Let g represent Greg's age, and write expressions for his age.
Check It Out!
Four times Greg's age, decreased by 3 is equal to 3 times Greg's age, increased by 7. How old is Greg?
Let g represent Greg's age, and write expressions for his age.
Four times Greg's age
three times Greg's age
is equal to
decreased by
increased by 3 7 .
4g – = g

20. Check It Out! Continued
To collect the variable terms on one side, subtract 3g from both sides.
4g – 3 = 3g + 7
–3g –3g
g – 3 =
Since 3 is subtracted from g, add 3 to both sides.
g =
Greg is 10 years old.

21. Lesson Quiz 1. 7x + 2 = 5x + 8 2. 4(2x – 5) = 5x + 4
Solve each equation.
1. 7x + 2 = 5x (2x – 5) = 5x + 4
3. 6 – 7(a + 1) = –3(2 – a)
4. 4(3x + 1) – 7x = 6 + 5x – 2 5.
6. A painting company charges $250 base plus $16 per hour. Another painting company charges $210 base plus $18 per hour. How long is a job for which the two companies costs are the same? 3 8
all real numbers 1
20 hours