If the area is 121in2, the side length is 11in=11/12 ft=0.91667 (approx) if the rectangle is a square.
If the rectangle isn't a square then the length of two sides will be one length, but, although the other two sides are the same length as each other, they will be different from the common length of the other sides. So the only time you can ask for a single side length for all 4 sides is when the rectangle is a square.