triangle a' b' c' is a dilation of the triangle abc.
what is the scale factor?

These triangles have scale factor 2 : 1 from big one to the small one.

Hope it helps.

The scale factor is 1/2.

Step-by-step explanation:

For this question, the scale factor would be 1/2. Since we are going from a larger triangle to a smaller one, we know the scale factor must be less than one. When you look at corresponding sides (such as AB to A'B' and BC to B'C'), you can see that the length of the dilated copy is half of the original side. For example, BC has a length of 9, and B'C' has a length of 4.5, or 4 and 1/2. 4.5 is half of 9, so the scale factor for this dilation is 1/2.