One of the sides of the rectangle is 18cm, its P = 80cm. Find the sides of the rectangle.

In order to find the sides of a rectangle, we will use the formula for finding the perimeter of a rectangle to compose and solve a linear equation.
To find the perimeter of a rectangle, use the formula:
P = 2 (a + b);
From the condition, we know that one of the sides of the rectangle is 18 cm, and its perimeter is 80 cm.
Let’s denote the second side of the rectangle with the variable x cm.
2 (x + 18) = 80;
x + 18 = 80: 2;
x + 18 = 40;
x = 40 – 18;
x = 22 cm length of the second side of the rectangle.