If |A|=22, |B|=13, and |A ∩ B|=2, how many elements are only in A?

Question: If |A|=22, |B|=13, and |A ∩ B|=2, how many elements are only in A?

1. 21
2. 20
3. 19
4. 22

Correct Answer: B — 20

Explanation: Subtract the elements shared by both sets from |A|.
Using the values in this question gives 20 as the correct answer.