How much greater is the median number of pairs of shoes in the inventory at the golf pro shop than the median number of pairs of shoes in the inventory at the tennis pro shop?

20

To get this answer, you find the median of the golf pro shop data (a = 40) and the median of the tennis pro shop data (b = 20). Then you subtract to get a-b = 40-20 = 20. The median of any box plot is the vertical line inside the box plot. 

The third box is a function