Answer: third from the top
Explanation:
The correct answer is third from the top.
Arranging numbers in ascending order:
15 17 17 17 18 18 18 19 19 19 21 21 22 23 24
Let's count how many times each number occurs in this series of numbers.
row of numbers
15 +
16 not
17 + + +
18 + + +
19 + + +
20 not
21 + +
22 +
23 +
24 +
25 not