Final answer:
To reframe the sandbox, you will need 6 feet of boards on one side. To reframe all sides, you will need 24 feet of boards.
Step-by-step explanation:
To find the length of the sides of the sandbox, we need to find the square root of the area. Since the area is 36 square feet, the length of one side is the square root of 36, which is 6 feet.
To reframe one side of the sandbox, you will need boards that are 6 feet long. Since the sandbox is a square, all four sides are equal. So, to reframe all sides, you will need boards that are 6 feet long on all sides.
In total, you will need 6 + 6 + 6 + 6 = 24 feet of boards to reframe all sides of the sandbox.