Solving two-step equations
The Maths Habit
1Solve x + 7 = 12
x = 5
2Solve x − 4 = 9
x = 13
3Solve 3x = 15
x = 5
The scales balance. Sam takes the cubes off the left pan. What happens? How can Sam make the scales balance again?
The left pan goes up. Take the same number of cubes off the right pan too. Do the same to both sides.
- Equation
- Two things that are equal, with an equals sign between them.
- Unknown
- A letter that stands for a number we do not know yet.
- Solve
- Find the value of the unknown.
1Get the x's on their own
− 3 both sides2x = 8
2Find one x
÷ 2 both sidesx = 4
Get the x's on their own. What do you do to both sides?
3x + 4 = 19
− 4 both sides
Which comes first?
2x + 8 = 18÷ 2 both sides− 8 both sides
− 8 both sides first
Solve 2x + 5 = 17
1Get the x's on their own
− 5 both sides2x = 12
2Find one x
÷ 2 both sidesx = 6
Answerx = 6
Solve 3x + 2 = 14
1Get the x's on their own
− 2 both sides3x = 12
2Find one x
÷ 3 both sidesx = 4
Answerx = 4
Solve 2x + 5 = 17
1Get the x's on their own
− 5 both sides2x = 12
2Find one x
÷ 2 both sidesx = 6
Answerx = 6
Solve 4x + 3 = 23
1Get the x's on their own
− 3 both sides4x = 20
2Find one x
÷ 4 both sidesx = 5
Answerx = 5
Remember1Get the x's on their own+ or − both sides2Find one x÷ both sides
Solve 2x + 5 = 17
1Get the x's on their own
− 5 both sides2x = 12
2Find one x
÷ 2 both sidesx = 6
Answerx = 6
Solve 5x + 1 = 31
1Get the x's on their own
− 1 both sides5x = 30
2Find one x
÷ 5 both sidesx = 6
Answerx = 6
Remember1Get the x's on their own+ or − both sides2Find one x÷ both sides
Solve 2x + 5 = 17
1Get the x's on their own
− 5 both sides2x = 12
2Find one x
÷ 2 both sidesx = 6
Answerx = 6
Solve 10x + 6 = 46
1Get the x's on their own
− 6 both sides10x = 40
2Find one x
÷ 10 both sidesx = 4
Answerx = 4
Remember1Get the x's on their own+ or − both sides2Find one x÷ both sides
Solve 3x + 5 = 20
1Get the x's on their own
− 5 both sides3x = 15
2Find one x
÷ 3 both sidesx = 5
Answerx = 5
Solve 4x + 2 = 30
1Get the x's on their own
− 2 both sides4x = 28
2Find one x
÷ 4 both sidesx = 7
Answerx = 7
Solve 5x + 3 = 43
1Get the x's on their own
− 3 both sides5x = 40
2Find one x
÷ 5 both sidesx = 8
Answerx = 8
Remember1Get the x's on their own+ or − both sides2Find one x÷ both sides
- A dashed tile takes away.
- 4x − 3 is four x's, take away 3.
- To undo − 3, + 3 both sides
Get the x's on their own. What do you do to both sides?
5x − 2 = 18
+ 2 both sides
Solve 3x − 2 = 13
1Get the x's on their own
+ 2 both sides3x = 15
2Find one x
÷ 3 both sidesx = 5
Answerx = 5
Solve 2x − 3 = 11
1Get the x's on their own
+ 3 both sides2x = 14
2Find one x
÷ 2 both sidesx = 7
Answerx = 7
Solve 3x − 2 = 13
1Get the x's on their own
+ 2 both sides3x = 15
2Find one x
÷ 3 both sidesx = 5
Answerx = 5
Solve 5x − 4 = 21
1Get the x's on their own
+ 4 both sides5x = 25
2Find one x
÷ 5 both sidesx = 5
Answerx = 5
Remember1Get the x's on their own+ or − both sides2Find one x÷ both sides
Solve 3x − 2 = 13
1Get the x's on their own
+ 2 both sides3x = 15
2Find one x
÷ 3 both sidesx = 5
Answerx = 5
Solve 3x − 5 = 16
1Get the x's on their own
+ 5 both sides3x = 21
2Find one x
÷ 3 both sidesx = 7
Answerx = 7
Remember1Get the x's on their own+ or − both sides2Find one x÷ both sides
Solve 3x − 2 = 13
1Get the x's on their own
+ 2 both sides3x = 15
2Find one x
÷ 3 both sidesx = 5
Answerx = 5
Solve 4x − 6 = 30
1Get the x's on their own
+ 6 both sides4x = 36
2Find one x
÷ 4 both sidesx = 9
Answerx = 9
Remember1Get the x's on their own+ or − both sides2Find one x÷ both sides
Solve 2x − 7 = 9
1Get the x's on their own
+ 7 both sides2x = 16
2Find one x
÷ 2 both sidesx = 8
Answerx = 8
Solve 5x − 3 = 32
1Get the x's on their own
+ 3 both sides5x = 35
2Find one x
÷ 5 both sidesx = 7
Answerx = 7
Solve 3x − 4 = 26
1Get the x's on their own
+ 4 both sides3x = 30
2Find one x
÷ 3 both sidesx = 10
Answerx = 10
Remember1Get the x's on their own+ or − both sides2Find one x÷ both sides
Is the first step right? Thumbs up: yes. Thumbs down: no.
3x + 5 = 26 − 5 both sides
Yes
4x − 7 = 13 − 7 both sides
No: + 7 both sides
2x + 6 = 20 ÷ 2 both sides
No: − 6 both sides
5x − 1 = 24 + 1 both sides
Yes
10x + 3 = 53 − 3 both sides
Yes
x = 4 is the answer to 3x + □ = 20. What number goes in the box?
8
I think of a number. I multiply it by 7. Then I take away 4. I get 45. What is my number?
7
Write your own equation with the answer x = 3. Use two steps.
For example 2x + 1 = 7
Solve 4x + 3 = 27. Step 1 is given: − 3 both sides, so 4x = 24.
Answer x = 6
Solve 2x − 5 = 13
Answer x = 9
Solve 5x + 2 = 37. Show your steps.
x = 7
Exit tickets to print