The diagonal of a rectangle is 10 inches long and the height of the rectangle is 8 inches. What is t

Draw this rectangle and you'll see we have a pythagorean theorem equation.

a^2 + b^2= c^2
b = 8 and c= 10
a^2 + 8^2 = 10^2
a^2 + 64 = 100

Subtract 64 from each side:
a^2 = 36
a= 6

Therefore, perimeter P is:
P = 2l + 2w
P = 2(6) + 2(8)
P = 12 + 16
P = 28