Answer: A. 15 feet
Step-by-step explanation:
The formula used to calculate the perimeter of a rectangle is:

Where "l" is the lenght of the rectangle and "w" is the width.
You know that the length of this rectangle is 4 times its width. This means that:

And you know that the perimeter is 150 feet.
Then, you need to substitute
and the value of the perimeter into the formula and solve for "w":
