<PRE><B>Question 573229</B>
The perimeter of a rectangular frame is W + W + L + L.  Or 2W + 2L.


You were given a couple important pieces of information for this problem.
First, P = 72 so
2W + 2L = 72
And you know the W = L + 4.


If we start with the first equation, 2W + 2L = 72 and substitute for W using the 2nd equation, we get:
2(L+4) + 2L = 72  Multiplying out the paren
2L + 8 + 2L = 72  Combining terms:
4L + 8 = 72   Subtracting 8 from each side of the equation:
4L = 64  dividing each side by 4:
L = 16


If the width is 4 more than the length, then 
W = 16 + 4 = 20


Checking:
2(16) + 2(20) = 72
32 + 40 = 72
72 = 72  Correct!


</PRE>