The length of a rectangle is 8 less than 5 time it's width. The width is increased by three while the length is unchanged. Using a as the variable, express the change in area in terms of a

Im not quite sure what is being asked. Are we simply supposed to calculate the area? If that is the case i end up getting 2(5w - 8) + 2(w + 3) my books says 15a - 24