The median of the data would be (20+25)/2, which is 45/2 = 22.5.
The first quartile (Q1), the middle number between the smallest number and the median of the data set, is 9.
The second quartile (Q2) is the median of the data. (22.5)
The third quartile (Q3) the middle value between the median and the highest value of the data, is 35.
Hope this helped!