frequency distribution student ages

frequency distribution student ages



age A=event the student selected is under 21
17 B=event the student selected is over 30
18 C=event the student selected is in his or her 20s, and
19 D=event the student selected is over 18
90
21
22
23
24
35
36

frequency
1
1
9
7
7
5
3
4
1
1
1



I'm really confused about the outcome of (b). it's asking student selected over 30 and there are two students over 30, nut the answer is (A&D) Please explain why (A&D) is the answer and how did they come up with that.