The perimeter of the rectangle is 18 cm; its length is 3 cm longer than the width of the sides of the rectangle.

Let’s solve this problem using the equation. Let us take an unknown value (the width of the rectangle) as x cm, then its length, by condition, will be equal to 3 + x cm.The perimeter of the rectangle is calculated by the formula (a + b) * 2, where a is the length, b is the width. Let’s make the equation:

(3 + x + x) * 2 = 18

(3 + 2x) * 2 = 18

6 + 4x = 18

4x = 18-6

4x = 12

x = 12/4

x = 3

3 cm is the width of the rectangle, so its length is 3 + 3 = 6 cm.

Answer: 3 cm and 6 cm.