Use inverse operations in reverse order. In 6x + 10 = 34, x is multiplied by 6 and then 10 is added. Undo the adding first: 6x = 24. Then undo the multiplying: x = 4.
Answers can be negative or fractions. In 4x + 15 = 3, subtract 15 to get 4x = −12, so x = −3. In 2x − 1 = 6, add 1 to get 2x = 7, so x = 3.5. Check by substituting the answer back into the original equation.
Worked example
Solve 5x − 8 = 27
- Add 8 to both sides: 5x = 35.
- Divide both sides by 5.
Answer:x = 7
Key words
- inverse operation
- the operation that undoes another
- solution
- the value that makes the equation true
- substitute
- put the value back in to check
Practise this
New questions every time.
Common Core-referenced: 7.EE.B.4a