First, notice that the two already labelled boxes have an area of 300 square feet each. Then, they account for a total of 600 square feet. Substract 600 from 726 to see how much additional area is needed:
Since the path is 3 feet wide, and the area of a rectangle equals length times width, then divide the area of 126 squared feet by 3 feet to find the remaining length needed:
Therefore, the length of the path needed to complete the sketch is:
