See picture for answer and solution steps.
The correct answer is 50%.
Approximately the middle 50% of data is contained inside the box of a box plot.
5/6 = .83333333333333333333333333.... It goes on...
.833333333333333333 * 18 = 15
15 is your answer
Another way you could do it is 18/6 = 3
3+3+3+3+3 = 15
3 being 1/6th of 18 *Hope This Helps...*
I believe that the answer for y is...
y= -ax+c/b