The area of a four square court is 66 square feet. estimate the side length, s, to the nearest tenth of a foot

Since it's a square court, all sides are equal, so we can square one side to find the area. S²=A

We know the area (66 ft²) but not the length of one Side...
Enter our known value, and take the square root of both sides:
S²=66
√S²=√66
S=√66
S≈8.12403round to the nearest tenth:
S=8.1 ft