Answer: Your new triangle would have the side lengths 3 m, 4 m, and 5 m.
Explanation:
To make a triangle 1/3 as long as the original, you can multiply each side length by 1/3 (or simply divide each side by 3) to get the new side lengths.
9 ÷ 3 = 3
12 ÷ 3 = 4
15 ÷ 3 = 5
Therefore, the new triangle would have side lengths of 3 m, 4 m, and 5 m.
I hope this helps! I attached a drawing of the triangle for reference c: