In set notation this is B = {1, 4, 9}. 30 people answered a survey about whether they have a dog or a cat. The Venn diagram shows the information from the survey. 13 people have got a dog.

It's possible a Venn diagram can have three (or more) sets depicted within them. A set of pupils were asked which sports they played in school, from a list of Football, Hockey, Netball and None.