I got 64 square feet.
My work is shown in the image.
For possible questions:
1: you can find x+7 and x-2 because the sides of the square can be measured as x, and x+7 means 7 more than the original; x-2 means 2 less than the original.
2: solved via factoring. Not sure if you've learned it or not.
3: reject the negative numbers because you can't have negative sides in a square.
(3/5)b - 7 = a
Remember "of" means to multiply. Less than means subtraction: 7 less than means -7.