In a recent survey of 100 women, the following information was gathered.

Question

42 use shampoo A.
38 use shampoo B.
34 use shampoo C.
7 use shampoos A and B.
9 use shampoos A and C.
11 use shampoos B and C.
5 use all three.

How many are using shampoos A and C, but not B?
_____women

Answer 1

9 use shampoos A and C. This set of 9 also includes people who would use B.

5 people use all three

9 - 5 = 4