Subtract 7.5 from 24 to get the remaining amount of wall that has no picture frame covering it. 24 - 7.5 = 16.5. You then would divide 16.5 by 2 as there are two sides on either side of the painting that need to be covered. 16.5 / 2 = 8.25. To check yourself: 8.25 + 8.25 + 7.5 = 24.
