Question 876711
set W = width
set L = W + 4
area = L*W
 20 = (W + 4)(W)
 20 = W^2 + 4W
add -20 to each side
 0 = W^2 + 4W -20
Using quadratic equation we get
W = {{{-2(1 + sqrt(6))}}} or {{{2( sqrt(6) - 1 )}}}
Since we need a positive length, the answer is {{{2( sqrt(6) - 1 )}}}
= 2.90 ft
Let's see if this reasonable.
W = 2.90 , L = 2.90 + 4 = 6.90
2.90 * 6.90 = 20.01 , so we are good