Read the data represented by the Venn diagram. For example, a teacher polls her students to see which flavors of ice cream they like. The choices are vanilla, chocolate and strawberry. Students may vote for one or more flavors.
Look at the central area of overlap to find the total that applies to all three circles. In this case, the number written in the central area of overlap would indicate the total of students that voted for all three flavors of ice cream.
Look at areas of overlap between two circles (assuming that there are three or more circles in the diagram) to find the shared total for those two subjects. In this example, look at the numbers written where the vanilla and strawberry circles overlap to figure out how many students voted for both of these flavors. You would use the same technique for the other shared areas of vanilla and chocolate, as well as for chocolate and strawberry.
Count all of the numbers represented on the entire diagram for an overall total. Numbers that appear in nonoverlapping areas are specific to the circles in which they appear. In this example, you would add the numbers appearing in each flavor circle, as well as all of the overlapping areas to find the total number of votes.