Answer: 38
Reason:
Your teacher wants you to find out how many elements are in set A.
Focus on the numerators only.
That sequence is 1,2,3,..., 37,38 which consists of 38 numbers.
If you wanted to focus on the denominators, then we go from 3 to 40 which is a gap of 40-3 = 37, but then add on 1 to account for the first item. So we get to 37+1 = 38.
