The Venn diagram shows the information from the survey. 13 people have got a dog. The circle for the set of people with a dog has 5 people who just have a dog and 8 people who have both a cat and ...

11 visitors have seen Band X and Band Y only. We can now fill this in on our diagram. If we now look at the Band Y circle, we have all the sections complete except one. Now add up the numbers we ...