Perimeter of a rectangle is found by finding the sum of the lengths of all four sides. We will call the two sides parallel that represent the length L and L and the two sides that represent the width W and W. We use the same variables because the opposite sides are equal to each other by definition of a rectangle. .
Perimeter = L + L + W+ W = 2L + 2W COMBINE LIKE TERMS
Width is 8 less than the length, W= L - 8
64 = 2 L + 2(L-8) SUBSTITUTION
64= 2L + 2L - 16 DISTRIBUTE
64 = 4L - 16 COMBINE LIKE TERMS
+16 = +16
80 = 4L
20 = L, W= L - 8 , W = 20 -8 , W = 12
SUBSTITUTE AND CHECK THE ANSWER 64 = 2*12 + 2*20 =24 + 40 = 64
