algebra · Year 6 · AC9M6A02

Equations with brackets

In 3(x + 2) = 21, the number outside the brackets multiplies everything inside. To solve it, undo the steps in reverse order. First divide both sides by 3 to get x + 2 = 7, then take 2 from both sides to get x = 5. Check by putting 5 back: 3 × 7 = 21. When x is on both sides, expand the brackets and take the smaller x term from both sides.

Sample questions

Solve for x: 4(x + 4) = 64

  1. 4 lots of (x + 4) make 64.
  2. Divide both sides by 4: x + 4 = 16.
  3. Take 4 from both sides: x = 12.

Answer: 12

Solve for x: 4(x + 9) = 68

  1. 4 lots of (x + 9) make 68.
  2. Divide both sides by 4: x + 9 = 17.
  3. Take 9 from both sides: x = 8.

Answer: 8

Solve for x: 4(x + 6) = 32

  1. 4 lots of (x + 6) make 32.
  2. Divide both sides by 4: x + 6 = 8.
  3. Take 6 from both sides: x = 2.

Answer: 2

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