Venn diagrams are two or more overlapping circles that show a relationship of a math set. These diagrams are a way to compare and contrast two or more items and organize data. Each circle has a set of information. At the intersection of the circles--where the circles overlap--are the items both sets have in common. Outside of the intersection are items the two sets do not have in common. Venn diagram math problems are presented in two ways: first, with the information displayed in the diagram, and you solve the problem based on the information; or with a blank Venn diagram, and you must use the given information to fill in the diagram.

1. Draw a Venn diagram based on how many circles you will need to solve the math problem. Create one circle for each group in the problem.

2. Label below each circle the names of the groups from the problem. Here's an example word problem: In a class of 70 students, 38 take physical education, 22 take music and three more take both PE and music. How many in the class are not enrolled in either? For this example, label one circle "Physical Education" and the other circle "Music."

3. Analyze the data you have been given in the word problem. Fill in the center of the Venn diagram first. Continuing the example, write the number 3 in the center, or overlapping section, because that is how many students take both classes.

4. Identify the information from the word problem that goes in the outer part of each circle. In the example, write the number 38 in the outer section of the "Physical Education" circle and the number 22 in the "Music" circle.
5. Add, subtract, multiply or divide, based on the specific problem, and check that the amounts in the circles are the same as the amounts in the question. Completing the example, add 38, 3 and 22. Then take the total of those three numbers--63--and subtract that number from 70, which is the total number of students. The answer--seven--will be the number of students who are not enrolled in either class.

Source: http://www.ehow.com/how_6944123_solve-venn-diagram-problems.html