9.354 ft is the answer. Here are the steps:
Area is 87.5 ft^2.
Take the square root of 87.5; each wall side is going to be the same length since it's a square. Since each side is the same length, it means one wall x another wall will give you the area.
This is the answer you get: 9.35414346693.
Round the number to make it look a little prettier: 9.354.
When you multiply 9.354 x 9.354, you get 87.497316.
Round the number again to make it look a little prettier: 87.5
Hope this helps. :)
