Answer:
C. 30
Explanation:
First, you want to make the two fractions have the same denominator. This means, that instead of saying that 1/3 of the dogs being large, you would say that 2/6 of the dogs are large. Then, combine the amount of large and medium dogs, making large and medium dogs 3/6 of all the dogs. The amount of small dogs must complete this fraction, so now we know that 3/6 of the dogs are small. This means half of the dogs are small dogs. Divide 60 by 2, and you have your answer.