Find the side of the rectangle if its perimeter is 40 cm and the length is 12 cm. Find out the area of this rectangle.

Let’s denote the width of this rectangle through x.

According to the condition of the problem, the length of this rectangle is 12 cm, and its perimeter is 40 cm.

The perimeter of any rectangle is equal to twice the sum of the length and width of this rectangle, therefore, we can make the following equation:

2 * (12 + x) = 40.

We solve the resulting equation and find the width of this rectangle:

12 + x = 40/2;

12 + x = 20;

x = 20 – 12;

x = 8 cm.

Find the area S of a given rectangle as the product of the length and width of a given rectangle:

S = 12 * 8 = 96 cm².

Answer: the area of ​​this rectangle is 96 cm².