Since the perimeter is 120 feet and it is a square, it means all 4 sides are equal and the perimeter should be divided by 4. Let the length be x
x = perimeter / 4
X = 120 / 4 = 30 feet each.
The length of each side is 30 feet.
Next, the area of the garden is x squared.
So the area is 900 square feet.