Arectangle has the length that is five times longer than it’s width. if the perimeter of the rectangle is 12 inches, whats the width?

The width would be 1 inch.

Given: L = length = 5W; P = perimeter = 2(L+W) = 12 inches
Required: W = width; 
Formula: P=2(L+W) 
Solution:
              12 in = 2 (L + W)
              6 in = L + W
              6 in = 5W + W
              6 in = 6W
              1 in = W
Cross check:
              P = 2(L + W)
              12 in = 2(5 in + 1 in)
              12 in = 2(6 in)
              12 in = 12 in