Answer: 35.5 (36.0 rounded)
First, you have to order the data set from lowest to highest.
25, 26, 28, 29, 29, 31, 31, 33, 33, 34, 37, 37, 38, 39, 43, 44, 45, 45, 48, 50
Then, you need to find the middle number in the above list of numbers. Since there are 20 numbers in total, there will be two middle numbers: 34 and 37.
Since there's an even amount of numbers, you must find the average of said two numbers.
Median = (34 + 37) ÷ 2 = 71 ÷ 2 = 35.5 ≅ 36.0