Hello Joseph,
The question asks for the total length of wood. In other words, you're asked to find the perimeter of the square box.
If every side of a square has length s, the perimeter of a square is P = 4s
How do we find s in the 1st place? You're given the area of the square box: 196 square feet.
Formula for area of a square: A = s2. So 196 = s2. If you solve that equation by taking the square root on both sides, you get 14 = s, so the square has sides that are 14 feet long.
Plug that answer into the formula for the perimeter to answer the original question: P = 4*14 = 56 feet.
The total length of wood Mrs. Drew needs to make the sides of the sandbox is 56 feet.