Answer:
Yes, the scale factor is 0.6 repeating, or 0.7.
Explanation:
You find the scale factor by dividing the smaller sides by the corresponding larger ones.
12/18 = 0.6 repeating
14/21 = 0.6 repeating
16/24 = 0.6 repeating
These triangles could be similar by SSS or SAS or ASA I think since congruent angles are shown in both triangles as well.