Answer:
C
Step-by-step explanation:
If you draw a straight line through all the corresponding vertices, where the three vertices meet up at is the center of dilation, they all meat up at point C so C is the center of dilation.
As we could "drag" these together, we could then do it the easy way.
56
+56
+56
-------
168
------------------------
Or we could also do the following:
56

3:
6

3= 18.
Carry the one.
5

3 = 15+1 (which was carried). = 16
(16+8) =
168