Answer:
40 ft.
Explanation:
Because James's yard is a square, we can take the square root of the area to find the side length. The square root of 100 is 10, so we know that one side of his yard will require 10 feet of fencing. Since the yard has 4 sides, we simply need to do 4 * 10 = 40 ft of fencing.
Hope this helps!