Hi. What is the area of a rectangle? It is given to you that x is the length. Lets call the height h. Try to connect the perimeter of the rectangle that is 100 meter with x and h and find an expression for h(x). Then find the area A(x). Make a graph and you will get the answer of what you are looking for. If you get stuck we will help you, but show us what you can do by yourself.