Answer:
18.5
Explanation:
Make sure the numbers are in order from least to greatest!
To define the median of the lower half, you must first divide the data set in half. Then, find the median of the first half.
17, 18, 19, 20 | 21, 24, 25, 27
To find the median, locate the number(s) in the middle of the data set.
17, 18, 19, 20
There are two numbers in the middle: 18 and 19.
When you have two medians, add the numbers, then divide the sum by 2.

The median of the lower half is 18.5.