How many possible 5-card hands from a deck of 52 cards are there that consists of 3 hearts and a three-of-a-kind?
C(13,3) = number of ways to choose three hearts
C(3,1) = number of ways to choose which heart gets to be part of the three-of-a-kind
C(3,2) = number of ways to choose 2 cards from the remaining suits to complete the three-of-a-kind.
So, in total, we have: C(13,3) * C(3,1) * C(3,2) possible hands.