In a parallelogram, the sum of the adjacent sides is 20 cm, and the difference is 12 cm. Find the sides of this parallelogram.

1. A, B, C, D – the tops of the parallelogram. AB + AD = 20 cm. AD – AB = 12 cm.

2. We take the length of the AB side as x, and the length of the AD side as y.

3. Let’s compose two equations:

x + y = 20;

y – x = 12.

4. Add these equations:

x + y + y – x = 32;

2y = 32;

y = 16.

AD = 16 cm.

AB = AD – 16 = 4 cm.

5. According to the properties of a parallelogram, its opposite sides are equal.

Therefore, AB = CD = 4 cm, AD BC = 16 cm.

Answer: AB = CD = 4 centimeters, AD = BC = 16 centimeters.