L is the length and W is the width of the rectangle. L = W + 3
The Perimeter = 2L + 2W = 2(W + 3) + 2W = 4W + 6
The Area = L W = (W + 3) W = W2 + 3 W
The Area and Perimeter are equal in value, so
W2 + 3 W = 4W + 6
Now the above quadratic equation for W and we substitute to find L btw
W = 3 and L + 6
I hope this helped!