Since the surface area takes places as a right triangle it would mean that it's half of a square so we know we should divide by 2 as the last step to finding the surface area. I take the length and the width and multiply them together. 3 times 7 equals 21 mm squared. 21 mm squared is the value and like I said. Your final step is to divide so I divide 21mm by 2 and I get 10. 5mm squared as my surface area. To get the height I simply multiply the length times the width times the height and divide by 2 since it's half of the area of a rectangle. 3 times 7 makes 21 and you multiply it again but this time with the height which is 6mm. 126 is the value we got. Our final step is to divide by 2 and we get the answer as 63 mm cubed.