Example:

What is the probability of feeding 3 monsters and getting exactly one skill up?

Permutation 1: 1 skill no skill no skill

Permutation 2: no skill 1 skill no skill

Permutation 3: no skill no skill 1 skill

Permutations=3



(.2^1)*(.8^(3-1))*3=.384 or 38% chance of getting exactly 1 skill-up when you feed three monsters to your baby.