Find the perimeter of the rectangle if its area is 18 cm2 and the length of one side is 3 cm.

First of all, you need to remember the formulas for the perimeter and area of a rectangle:

P = 2 * (a + b);
S = a * b,

where P is the perimeter of the rectangle,
S – area of the rectangle,
a and b are the sides of the rectangle.

Then, knowing one of the sides (a = 3 cm by condition), you can find the second side by expressing it from the area formula:

b = S: a = 18: 3 = 6 (cm).

Now, knowing the lengths of the two sides of the rectangle with different lengths, you can calculate its perimeter:

P = 2 * (3 + 6) = 2 * 9 = 18 (cm).

Answer: P = 18 (cm).