A I think is the right answer
I am going to assume you mean 56 SMALL dogs in the show. If you do, your answer is 42 large dogs.
We're told that



a. We want to find
. By definition of conditional probability,

By the law of total probability,

Then

(the first equality is Bayes' theorem)
b. We want to find
.

since
.
Its the third pair of inequalities
b 26 < n < 30
so n = 28
the 3 numbers are 28, 30 and 32