Answer:
w² + 5w = 36
Explanation:
Since the pen is a rectangle, its area, A = lw where l = length and w = width.
Since the length of the fence is 5 feet longer than its width, we have l = w + 5
So, A = lw = (w + 5)w = w² + 5w
Since A = 36 ft², we have that
36 = w² + 5w
w² + 5w = 36
Which is the required equation.