1. Objective The student will be able to:
solve two-step equations.
SOL: 8.15a
Designed by Skip Tyler, Varina High School

2. To solve two-step equations, undo the operations by working backwards.
Recall the order of operations as you answer these questions.
Dividing by 2
Subtracting 3
Example:
Ask yourself,
What is the first thing we are doing to x?
What is the second thing?
To undo these steps, do the opposite operations in opposite order.

3. Use a DO-UNDO chart as a shortcut to answering the questions
Use a DO-UNDO chart as a shortcut to answering the questions. In the table, write the opposite operations in the opposite order
DO UNDO ÷2 -3
Follow the steps in the ‘undo’ column to isolate the variable.
Draw “the river”
Add 3 to both sides
Simplify
Clear the fraction -Multiply both sides by 2
Check your answer +3
· 2
= - 4
x = -8
-4 – 3 = -7
2 · · 2

4. 1) Solve 2x - 1 = -3 + 1 + 1 2x = -2 2 2 x = -1 2(-1) - 1 = -3
D U
1) Solve 2x - 1 = -3
· 2
- 1
+ 1
÷ 2
2x = -2
x = -1
2(-1) - 1 = -3
-2 – 1 = -3
Draw “the river”
Add 1 to both sides
Simplify
Divide both sides by 2
Check your answer

5. 2) Solve + 4 + 4 3 · · 3 x = 36 12 – 4 = 8 D U Draw “the river”
÷ 3
- 4
+ 4
· 3
3 · · 3
x = 36
12 – 4 = 8
Draw “the river”
Add 4 to both sides
Simplify
Clear the fraction -Multiply both sides by 3
Check your answer

6. 3) Solve 3y – 1 = 8
y = 3
y = -3
y =
Answer Now

7. 3) Solve d = 10 d – 4 = 6 + 4 + 4 D U Draw “the river”
- 4
÷ 2
· 2
+ 4
Draw “the river”
Clear the fraction - Multiply both sides by 2
Simplify
Add 4 to both sides
Check your answer
d – 4 = 6
d = 10

8. 4) Solve
d = -7
d = -19
d = -17
d = 17
Answer Now

9. 5) Solve -3 -3 a = 35 D U Draw “the river” Subtract 3 from both sides
÷ -7
+ 3
- 3
· -7
Do/Undo Chart – This one is tricky! Remember to always use the sign in front of the number.
a = 35
Draw “the river”
Subtract 3 from both sides
Simplify
Clear the fraction – Multiply both sides by -7
Check your answer

10. 6) Solve 5z + 16 = 51
z = -35
z = -7
z = 35
z = 7
Answer Now

11. 7) Solve - 1 - 1 5 · · 5 3x = 15 3 3 x = 5 D U Draw “the river”
· 3
÷ 5
+ 1
- 1
· 5
÷ 3
5 · · 5
3x = 15
x = 5
Draw “the river”
Subtract 1 from both sides
Simplify
Clear the fraction -Multiply both sides by 5
Divide both sides by 3
Check your answer