Question 51327
I assume that you meant to write..."Each pen will be three times as long as it is wide,..."
If we let the width be W, then the length of each pen will be: L = 3W.

From the problem description, the two adjacent pens will have three long sides and four short sides.
Each long side will be 3W in length and there are three of these,
so we have 3(3W) = 9W. This is the total of the lengths.
The short sides (Widths) wll each be W in length and there are four of these, so we have 4(W) = 4W This the total of the widths.
Adding up all of these, we get:
9W + 4W = 13W and this is equal to the total length of the fence (perimeter) of 65 feet.
13W = 65 Divide both sides by 13.
W = 5 feet.
This is the length of each width, but there are four of these, so we have the total for the widths is: 4(5) = 20 feet.
The length, L = 3W = 3(5) = 15 feet
The three lengths is then: 3(15) = 45 feet.

Each pen measures: (L X W) = 15 ft. by 5 ft.

Check:
Adding up the the total widths and the total lengths, we get: 20 ft + 45 ft = 65 ft.