Question 303732
Let's length be L and width be w

w = L - 3 

Area = L(L-3) = 54 

L(L-3) = 54
L^2 - 3L = 54
L^2 - 3L - 54 = 0

(L-9)(L+6) = 0

L-9 = 0 
L = 9 cm

or 

L + 6 = 0 
L = -6(N/A)

w = L - 3 
  = 9 - 3 
  = 6 cm

Answer Length is 9 cm and 6 cm