Dave and Jane Wells have a new rectangular driveway. The perimeter of the driveway is 168 feet. The length is 12 feet longer than three times the width. What are the dimensions of the driveway?

Let the width be represented by w and the length by l.

You are told the perimeter is 168 feet. And you know the perimeter of a rectangle is given by 

You are told  

Now using those two equations, solve for w as follows:

Now find l

Check your answer. Does