Answer:
90 feet
Step-by-step explanation:
The perimeter is the sum of the side lengths of the enclosure. The length is given as 80 ft, but only one side that long counts as part of the 260 ft of fence. So, we have ...
260 ft = 2×W + L = 2×W + 80 ft . . . . . length of fence for 3 sides
180 ft = 2×W . . . . . . subtract 80
90 ft = W . . . . . . . . . divide by 2
The width of the enclosure is 90 feet.
