Explanation:
Surface Area Formula: SA=2lw+2lh+2hw
SA is surface area. l is length, w is width, h is height. Make sure to follow PEMDAS and keep multiplication together before adding.
Now substitute values
2(12 3/4*8 1/2)+ 2(12 3/4 * 5 1/2)+ 2(5 1/2*8 1/2)
SA=450.5 inches squared