If the perimeter of a rectangle is 38 ft and the width is 9 ft, find its length. [Hint: The perimeter of a rectangle is given by P = 2L + 2W.]

I don't know why this is a problem for you. P = 38 and W = 9. Solve for L. You have only one unknown in the equation. If you don't know what to do next, please explain why you don't know how to proceed.

Let P = 38 and W = 9 and solve the perimeter equation "hint" for the length, L. As DrBob222 has stated, it is just a matter of plugging in the numbers and solving for the single unknown, L.