The length of the rectangle is 12 cm, which is 3 cm longer than its width. Find the perimeter of the rectangle?

1. To find the perimeter, you need to find the width of the rectangle. We find the width of the rectangle if it is known that it is less than the length by 3 cm, for this we subtract 3 from the length:
12 cm – 3 cm = 9 cm.
2. Find the perimeter of the rectangle by the formula P = 2 * (a + b), where P is the perimeter, a is the length, b is the width:
P = 2 * (12 cm + 9 cm) = 2 * 21 cm = 42 cm.
Answer: The perimeter of the rectangle is 42 cm.