Question 301000
<b>Variables Used</b><ul>
	<li>p = perimeter</li>
	<li>l = length</li>
	<li>w = width</li>
</ul>
What do we know? We know that:
p = 64 cm
l = 2w - 4  
and finally we know that 
p = 2(l + w) or 2l + 2w <br>
so we will substitute 2w - 4 for l in the formula:
p = 2(2w - 4) + 2w
Now we will distribute:
p = 4w - 8 + 2w
combine like terms:
p = 6w - 8
I like working on the left,  so we'll flip-flop (advanced mathematical term) and replace "p" with 64:
6w - 8 = 64<br>
Add 8 to each side:
6w = 72
divide each side by 6:
{{{ cross(6)w/cross(6) = 72/6 = 12 }}} so 
w = 12
now remember that l = 2w - 4, and substitute 12 for 'w'
{{{ l = cross(2(12)) 24 - 4 = 20 }}}
l = 20

Your answers are 
Length = 20 cm
Width = 12 cm & bob's your uncle!