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.

Notice you don’t use capitals within the brackets. A Venn diagram begins with a box called our universal set, which is denoted by the symbol \(ε\) (epsilon). The universal set contains ...