Dogs are $$\frac{1}{3}$$ of all animals, so $$\frac{2}{3}$$ remained. Cats are $$\frac{1}{6}$$ of the remainder, hamsters are the rest.
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• Dogs → $$\frac{1}{3}$$ of whole = $$\frac{6}{18}$$
• Remainder → 1 − $$\frac{1}{3}$$ = $$\frac{2}{3}$$ = $$\frac{12}{18}$$
• Cats → $$\frac{1}{6}$$ × $$\frac{12}{18}$$ = $$\frac{2}{18}$$ → 2u
• Hamsters → 12u − 2u = 10u
• Dogs − Cats → 6u − 2u = 4u → 12 animals ⇒ 1u = 3 ⇒ Total = 18 × 3 = 54
There are 54 animals in the shop.
Check: Dogs = 6 × 3 = 18. Cats = 2 × 3 = 6. 18 − 6 = 12. ✓