Find the perimeter of triangle ABC if side AB is 14 cm, BC is twice the size of AB, and AC is 7 cm less than BC.

1) Let us find out what is the length of the BC side, if we know that the AB side is 2 times shorter than the BC side, and the AB side length is 14 cm.

14 * 2 = 28 cm.

2) Determine the length of the AC side if we know that the BC side is 7 cm longer than the AC side, and we found out the BC side length and it was 28 cm.

28 – 7 = 21 cm.

3) Find out the sum of the lengths of all sides of the triangle, which will make up its perimeter.

28 + 21 + 14 = 63 cm.

Answer: the perimeter of this triangle was 63 cm.