Question

A farmer plans to use 180 ft of fencing to enclose a rengular region, using part of a river bank instead of fencing on one side. (a) find the area A of the region if the length of the side parallel to the river bank is four times the length of an adjacent side (b) find the area A of the region if the length of the side parallel to the river bank is one-fourth the length of an adjacent side (c) find the area A of the region if the length of the side parallel to the river bank is the same as the length of an adjacent side