Final answer:
The area of a square with a side length of 9 feet is 81 square feet.
Step-by-step explanation:
The area of a square can be found by multiplying the length of one side by itself. In this case, the side length is 9 feet, so the area of the square would be 9 feet * 9 feet = 81 square feet.
Learn more about Calculating the area of a square