A Venn diagram is a graphic that uses overlapping ... of using diagrams to illustrate the branch of mathematics known as set theory. In 1866, he published a groundbreaking work, "The Logic of ...

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.