Answer:
length = 13 ft
Width = 3 ft
Explanation:
Width = w ft
Length = ( w +10 ) ft
Area = 39 square ft
length * width = 39
(w +10)* w = 39
w *w + 10*w = 39
w² + 10w - 39 = 0
w² + 13w - 3w - 3*13 = 0
w(w + 13) - 3(w + 13) = 0
(w + 13) (w - 3) = 0 {Ignore w + 13 , as measurement cannot be in negative}
w - 3 = 0
w = 3
length = 3 +10 = 13 ft