The answer is below.
Work Step by Step
In order to solve this using one variable, we use a similar technique to the one that the book uses to solve the problem, but we do not use a systems of equations. Rather, we can call one side x, meaning that the other side is x+2. Thus, we set up the expression: $ 35 = x(x+2)$ We can then solve this as the book does to find the width. Next, we add two to find the length.