I've never even seen a box and whiskers plot should be pretty straight forward though.

So a box and whiskers plot is relatively simple if you know how to do it.

The left whisker ending, which is at 35, signifies the minimum.

The right whisker ending, which is at 99, signifies the maximum.

The middle line, at 68, is the median.

And the edge of the box on the left, at 50, is the First Quartile. (If you don't know what that is, basically the marker in between the first quarter and the second quarter)

And the edge of the box on the right is the Third Quartile, (Same thing except in between the third quarter and fourth)

So since the question is asking how many students scored better than an 85, and we know that 85 is the third quartile here, we know that 1/4 of the students scored better than an 85.

(So basically each section is 1/4 of the data set)

And 1/4 of 24 is 6.

So 6 students scored better than an 85.