The length of the rectangle is 84 cm. How much will the area of the rectangle decrease if its width is reduced by 5 cm?

Let’s denote the initial value of the rectangle width as x cm.

In this case, the initial area of the figure will be equal to:

84 * x cm2

If = we reduce the width by 5 cm, it will be:

x – 5 cm.

Thus, the area of the new figure will be:

84 * (x – 5) = 84 * x – 420 cm2

To determine the difference in the area of the figure, subtract a new one from the initial area.

As a result, it will be:

84 * x – (84 * x – 420) = 420.

Answer: The area of the rectangle will decrease by 420 cm2.