Find the perimeter of an isosceles triangle, the base of which is 12 cm, and the lateral one is 3 cm larger than the base.

Let us determine what value the length of the lateral side of a given triangle will correspond to, when it is precisely known from the condition of our problem that it is 3 centimeters greater than the length of the base of the same triangle:

12 + 3 = 15.

Let us determine what value in this case will correspond to the perimeter of our isosceles triangle (it is known to be equal to the sum of all sides):

12 + 15 * 2 = 12 + 30 = 42.

Answer: With such initial conditions, the perimeter of our triangle will be 42 cm.