The length of the rectangle is 12 cm, and the width is a quarter of the length. Find the perimeter of the rectangle.

Using general mathematical rules and formulas, for the case considered in the initial task, we get:

1) define the value of the width of the rectangle:

b = 1/4 * 12 = (12 * 1) / 4 (cm) = 12/4 (cm) = (3 cm).

2) Find the perimeter of the rectangle, taking into account that its value is determined as the sum of the lengths of the sides of the rectangle:

P = 3 (cm) + 3 (cm) + 12 (cm) + 12 (cm) = 6 + 24 = 30 (cm).