The idea, step by step
Undo a multiplication
The expression means . In , four equal groups have a total of 28. Divide both sides by 4 to find one group: .
The coefficient is the number multiplying the variable. Divide by that whole coefficient, not by one digit chosen from it. For example, is undone by dividing both sides by 12.
Undo a division
In , the unknown has been split into five equal groups. Each group contains 8. Multiply both sides by 5 to recover the original total: .
A fraction bar also means division: is the same equation. Keep the numerator, denominator and equals sign clear. Check by dividing your final value by 5 to see whether the original equation is true.
A common trap
For , subtract 5 because 5 is next to x.
Instead: means multiplication, so use division: . Subtracting 5 would undo a different operation.
See the thinking
Find one equal group
Solve .
- The variable is multiplied by 7.
- Divide both sides by 7: .
- .
- Check: .
Recover the full collection
Solve .
- The variable has been divided by 6.
- Multiply both sides by 6: .
- .
- Check: .
Check your understanding
Solve .
Show answer
.
Multiply both sides by 8: . Check: .
Your turn
6 questions · 13 marks · Work at your own pace.
Read the questions online
- Solve .2 marks
- Solve .2 marks
- Solve .2 marks
- Solve .2 marks
- Solve .2 marks
- Six identical packs contain 42 cards in total. Let be the number of cards in each pack. Write and solve an equation.3 marks
Read the worked solutions
Equivalent correct methods earn the corresponding marks. Include units where asked.
- Solve .2 marks
Divide both sides by 3.
.
Check: .
- Solve .2 marks
Divide both sides by 8.
.
Check: .
- Solve .2 marks
Divide both sides by 12.
.
Check: .
- Solve .2 marks
Multiply both sides by 5.
.
Check: .
- Solve .2 marks
Multiply both sides by 9.
.
Check: .
- Six identical packs contain 42 cards in total. Let be the number of cards in each pack. Write and solve an equation.3 marks
Six equal pack amounts give .
Divide both sides by 6: .
Check: .
; cards per pack.
Curriculum reference & lesson scope
Australian Curriculum v9 / SA Curriculum
Year 7 linear equations with natural-number solutions: equality, inverse operations, substitution checks and familiar models. Formal variables-on-both-sides techniques are not required here.
Official curriculum source ↗