Answer :
Length = x + 6
Width = x
Area = 16 ft^2
The formula needed is A = L•W.
Here is the set up:
16 = (x + 6)(x)
16 = x^2 + 6x
x^2 + 6x - 16 = 0
Solve for x. After finding x, plug into the definition I gave above for length and width to find your answer.