Afarmer is using a barn as one side of a fence to enclose his cattle. if the barn is 80 feet long what is the width of the rectangular enclosure if the farmer has 260 ft. of fencing to complete the project?

  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.