At the Zoo

Say 90 students go to the zoo. Three have a hot dog, soda and a Popsicle; 24 have a hot dog; five have a hot dog and soda; 33 have a soda; 10 have a soda and Popsicle; 38 have a Popsicle; eight have a Popsicle and hot dog. How many had nothing?

Source: Parade, Ask Marilyn, May 27, 2007