looking at the box plot,
the line at the middle of the rectangle represents the median
the end of the rectangle on the left represents the first quartile, q1
the end of the rectangle on the right represents the third quartile, q3
From the graph,
q1 = 65
q3 = 90
Interquartile range, q2 = (q3 - q1)/2
Interquartile range = (90 - 65)/2 = 12.5