Harriet wants to put up fencing around 3 sides of her rectangular yard and leave a side of 20 feet unfenced. If the yard has an area of 680 square feet, how many feet of fencing does she need?

My Effort:

A = L*W

A = 680 feet^2

L = 20 feet

680 = 20W

680/20 = W

34 = W

One side of the rectangular yard is 20 feet less.

So, P = L + 2W.

P = 20 feet + 2(34 feet)

P = 20 feet + 68 feet

P = 88 feet

Correct?