It helps to draw it all out. Draw the rectangle, if we don’t know what the width is we will call it x or whatever letter you like. Now that we call the width x, we know that the on length will be 4 more. There are two widths and lengths in a rectangle. After you drew it, you can see you’ll be able to set it all up to find the sun off all sides aka the perimeter. Here’s what that would look like(sorry I had to use my phone)