Can you explain how to solve this math problem: A small pizza can gives 4 slices, and a large pizza gives 8 slices.  George purchased 3 small and 2 large pizzas.  George would like to eat 3 pieces.  His friend Bob would like to eat one more piece than George.  Susie will eat half as many as Bob.  Bill, Fred and Mark would each like 3 pieces.  How many slices of pizza will be left over?