The animals are 9 equal units. Seven of them are dogs, totalling 21.

Animals333333333dogs 21 = 7 units

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

  1. 7 units → 21
  2. 1 unit → 21 ÷ 7 = 3
  3. All animals = 9 units → 9 × 3 = 27

There are 27 animals in the shop.

Check: 7⁄9 of 27 = 21 dogs. ✓