to find surface area, we have to find the area of each surface of the shape.
to find the side’s area, multiply length x width (9 x 4). the side rectangle = 36 cm^2
to find the back side’s area, multiply 4 x 5 = 20 cm^2
now, just multiply each of those based on how many times each appear in the figure
there are 4 rectangles congruent to the front one - so 4 x 36 cm^2 = 144 cm ^2
there are 2 rectangles congruent to the back one - so 2 x 20 cm^2 = 40 cm^2
now that we have the area of all the surfaces, simply add them together: 40 cm^2 + 144 cm^2 = 184 cm^2
SA = 184 cm^2
