The perimeter of the parallelogram is 60 cm, one of its sides is 6 cm smaller than the other. Find the side of the parallelogram.

In order to find the sides of a parallelogram, we will compose and solve an equation with one variable.
The condition says that the perimeter of the parallelogram is 60 cm. It is also known that one of its sides is 6 cm less than the other.
We denote by the variable x cm the length of one of the sides of the parallelogram, then the length of the second side can be written as (x – 6) cm.
The perimeter of a parallelogram can be found using the formula:
P = 2 (a + b);
2 (x + x – 6) = 60;
2x – 6 = 60: 2;
2x = 30 + 6;
2x = 36;
x = 36: 2;
x = 18 cm, then 18 – 6 = 12 cm.
Answer: 18 cm and 12 cm sides of the parallelogram.