Question

how do i calculate the surface area of a rectangular prism?

Answer 1

saurface are of the two 'ends' = x * y * 2
then there are four longer rectangles
their surface area = 2 * (x * l) + 2 * (x* l)

where l = length of longest side
and x and y are the 2 sides of the 2 ends.

Answer 2

total area = 2(x*y) + 2(x*l) + 2(y*l)