Answer:
S=2lw+2lh+2wh
Step-by-step explanation:
If we consider the structure of a box with length l, width w, and height h, we may note that it is formed from six rectangular faces. The bottom and top faces are rectangles with sides of length l and w. Two of the side faces have side lengths l and h. And the remaining two side faces have side lengths w and h.
As the area of a rectangle is the product of its side lengths, we can put this together to get the surface area S of the box as
S=2lw+2lh+2wh
