Me someone plz
in this problem

If the surface area of the entire pool is 210 square feet, and if one side is 10 feet, and base times width equals area, then all you have to do is do 210 divided by 10, which would mean the long side is 21 feet. To find the unknown measurement, take the known measurement, 9 feet, and do 21-9, which equals 12. So d=12 feet.