Question 245631
n = length
w = width

2w = n

2w * w = 648

2w + w^2 = 648
-2w         -2w
w^2 = 648-2w
*2       *2

2w^2 = 1296 - 4w
Square both sides
solve

w = 18
n = 36

P = 2n + 2w
P = 108