algebra
posted by Anonymous on .
a survey of 70 customers was taken at a bookstore regarding the type of books purchased. the survey found that 42 customers purchased mysteries,35 purchased science fiction, 28 purchased romance novels,19 purchased mysteries and sicence fiction, 15 purchased mysteries and romance novels, 11 purchased science fiction and romance novels and 4 purchased all 3 types. how many purchased only romance novels?

You solve this by creating a Venn Diagram with 3 intersecting circles.
Begin by putting the 4 where the 3 circles intersect.
When you are done, add up each part of all of the circles and you should get 70. If you get less than 70 that means customers purchased none of these and the difference between your total and 70 goes out side the circles.