Answer:
9.6 cm
Explanation:
Since the scale factor is 3 (you can figure that out by dividing the larger side of the triangle by the one on the smaller triangle that is the same side) you would divide all other sides by 3 to find individual lengths.
9.6/3 = 3.2
7.2/3 = 2.4
We already know the other side, 4.
3.2 + 2.4 + 4 = 9.6cm