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

It is known from the condition that the perimeter of the rectangle is 40 cm, and the length of the rectangle is 12 cm. In order to find the area of the rectangle, we need to know the length and width of the rectangle.

Let’s remember the formula for finding the perimeter of a rectangle:

P = 2 (a + b), where a and b are the length and width of the rectangle, respectively.

Substitute the known values and proceed to solving the linear equation.

2 (12 + x) = 40;

12 + x = 40: 2;

12 + x = 20;

x = 20 – 12;

x = 8 cm width of the rectangle.

We look for the area of the rectangle by the formula:

S = a * b = 12 * 8 = 96 cm2.