The 50th percentile is the median so the z score will be 0
One cat has four paws, so there are 120/4=30 cats. If a "set" of cats is two uncool cats and three cool cats, there are five cats in a set, so there are 30/5=6 sets. Since each of the six sets contains three cool cats, there are 18 cool cats in the family.
A = 1/2 b h
5 = 1/2 (5) h
10 = 5h
h = 10/5
h = 2
answer
2