You can divide this composite shapes in two shapes: the rectangle and the triangle. The rectangle has an area of width x height = 6x8=48 in^2. The triangle has an area of 0.5 x width x height = 0.5x(6-4)x(13-8)=0.5x2x5=5 in^2. If you add this up, you got 48+5=53 in^2, which is the total area.