Hi,
Alan knows he has 18 feet of plastic edging to use for the Perimeter.
and knows 18=2L+2W
2L+2W = 18
2(L + W) = 18
L + W = 9 (Various lengths and widths can be used as long as their sum is 9)
Using the Lengths Given:
L W
3 6
4 5
5 4
6 3
Wish You the Best in your Studies.