Find the perimeter of the triangle if side AB is 15 cm, side BC is 8 cm longer, and side AC is 5 cm less than side BC.

1) How long is the BC side?

By the condition of the problem, the BC side is 8 cm longer than the AB side, so the BC side length is

15 + 8 = 23 (cm).

2) How long is the speaker side?

According to the condition of the problem, the AC side is shorter than the BC side by 5 cm, then the AC side length is

23 – 5 = 18 (cm).

3) What is the perimeter of triangle ABC?

We find the perimeter of the triangle ABC by the formula P = AB + BC + AC, we get

15 + 23 + 18 = 56 (cm).

Answer: The perimeter of triangle ABC is 56 cm.