The sides of the rectangle are 8 cm x cm and its perimeter is 20 cm. Make an equation and find the unknown .

The sides of the rectangle are 8 cm x cm and its perimeter is 20 cm. Make an equation and find the unknown side of the rectangle.

In the problem statement, we were asked to compose equations and use it to calculate the length of the unknown side of the rectangle.

In the condition, we are given the lengths of one of the sides of the rectangle and its perimeter.

And also in the condition we immediately indicated the length of the unknown side by x cm.

We begin to compose an equation by recalling the formulas for finding the perimeter. Based on it, we will compose the equation:

P = 2 (a + b);

Substitute the values:

2 (x + 8) = 20;

x + 8 = 20: 2;

x + 8 = 10;

x = 10 – 8;

x = 2 cm length of the unknown side.