Answer:
3
Explanation:
you can set up a ratio using corresponding parts from each triangle.
or
notice the change from 3 to 9 is by multiplying 3 x 3
the change is the same for all : 3 x 4 = 12 , 3 x 5 = 15
ratio way
= = 3
the scale factor is 3. hope this helps
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= 3