Girls are 3 equal units = 21. Boys are 2⁄3 of the girls, so 2 of those units.

Girls777Boys7721

Plain numbers are given; italic underlined numbers are worked out.

  1. Girls = 3 units → 21
  2. 1 unit → 21 ÷ 3 = 7
  3. Boys = 2 units → 2 × 7 = 14

There are 14 boys.

Check: 2⁄3 of 21 = 14. ✓