A room is 15 feet tall. An architect wants to include a window that is 6 feet tall. The distance between the floor and the bottom of the window is b feet. The distance between the ceiling and the top of the window is a feet. This relationship can be a described by the equation a = 15 − (b + 6). If the architect wants b to be 3, what does this mean? What value of a would work with the given value for b ?