Let l be the length of the fence and w be the width. you know that lenth is approximately 1.6 times width, so you have your first equation: . Since there's 78 feet of fence available, and fence is a rectangle, which means that it has 4 sides (2 length and 2 width), , now you have your second equation which means you'll be able to solve for both variables by method of substitution or addition and after solving it for l and w, you will have the dimensions of the fence.