Answer: 80 feet.
Step-by-step explanation:
You can calculate the width using two equations and solving for the side lengths.
You can then substitute the L in the first equation for the L in the second equation:
Now, you can factor this equation to solve it:
Your solutions for W are -100 and 80. Considering the width of a rectangle cannot be negative, the only possible solution is 80 feet, which makes your length 100 feet.