Which expression represents the area of a rectangle with length l and width w?

The area of a rectangle is calculated by multiplying its length by its width. Therefore, if the length of the rectangle is represented by l and the width is represented by w, the formula for the area can be expressed as the product of these two dimensions, which is lw. This is a fundamental concept in geometry where the area provides a measure of the space contained within the boundary of the rectangle.

The other choices reflect different mathematical concepts but do not provide the correct calculation for area. For example, the perimeter of the rectangle is calculated with the expression 2(l + w), rather than the area. Similarly, adding or subtracting the length and width (l + w or l - w) does not yield the area of the rectangle, as those operations do not account for the two-dimensional nature of area calculation. Thus, the expression that accurately represents the area of a rectangle, given its length and width, is lw.