For this chain-of-thought reasoning and answer, what was the question?
Let S be the length of the short side of the fence. Thus, the length of a long side of the fence is 3S. There are 2 of each side, so the whole fence is 2S + 2 * 3S = 2S + 6S = 8S long. The whole fence is 8S = 640 feet long. Thus, the short side of the fence that needs to be replaced is S = 640 / 8 = 80 feet long.
 A: 80
Q: A rectangular plot of private property is fenced in by a chain-link fence. The long sides of the plot are three times the length of the short sides. One short side of the fence is rusted from being hit by a sprinkler and needs to be replaced. If all the sides of the fence together are 640 feet long, how many feet of fence need to be replaced?