Question

A, B, C are circular regions as shown below. There are 7 items in C and there are 20 items in A but 10 of those items are not in B. How many items are in B that are not in C

Answer 1

3 items are in B that are not in C

Explanation:

a: only in a, not count those in b or c

b: only in b, not count those in a or c

c: only in c, not count those in a or b

A = a + b + c = 20

c = 7

a + b = 20 - 7 = 13

10 not in b, of course not in c ∴ a = 10

b = 13 -10 = 3