Answer: Width = 45 feet; Length = 15 feet;
Step-by-step explanation: Start by substituting 3w for the length because it says that in the problem. We know that 2(L+W) equals the perimeter. Since we substituted 3w for length we get 8w for the perimeter. Divide 120 by 8 to find that the width is 15 feet and plug it into 3w to get the length of 45 feet.