Answer:
3
Explanation:
To find scale factor, you need to divide two of the given sides. Meaning you can do any corresponding sides. So, for now, I will do 12 from DEF and 4 from ABC.
12 ÷ 4 = 3
To check if it is accurately 3, you will do it again (optional). You can use 15 from DEF and 5 from ABC
15 ÷ 5 = 3
Since both are 3, that will be the scale factor.
The answer is 3.