Calculate the area of a rectangle whose length is 80 mm and the width is 40 mm less.

Let’s find the width of this rectangle.
According to the condition of the problem, the length of this rectangle is 80 mm, and its width is 40 mm less, therefore, the width of this rectangle is:
80 – 40 = 40 mm.
Knowing the length and width of a given rectangle, we find its area S as the product of the length and width of this rectangle:
S = 80 * 40 = 3200 mm² = 32 cm².
Answer: the area of this rectangle is 32 cm².