Calculating the Area of a Rectangle

In a rectangle, the length is represented by l and the width is represented by w. The area of the rectangle is given by the formula:

$$A = l imes w$$

This rectangle's length is twice its width. If the perimeter of the rectangle is 48 units, what is the expression for the area of the rectangle in terms of w? Additionally, calculate the area when the width is equal to 8 units.