We know that the width of the garden is = feet = 6.75 feet
and Perimeter of the garden is = 37.5 feet
Also, we know that for a rectangular space perimeter = 2 * (l + w)
⇒ 37.5 = 2 * (l + 6.75)
⇒ 37.5 = 13.5 + 2*l
⇒ 24 = 2*l
⇒ l = 12 feet
Now, we need to determine how much square feet of mulch is required, hence we need to calculate the area of the garden
Area = l * w
⇒ Area = 12 * 6.75
⇒ Area = 81 square feet
Hence, they require 81 square feet of mulch