We need to translate the points under the rule (x+18) and (y-12).
The points are given by the x-coordinate and y-coordinate following the form (x,y).
Now, let us use this rule for each point:
A.(-6,15)
Under the translation rule (-6+18,15-12) = (12,3)
So, A'=(12,3)
For B(-8,7)
Under the translation rule (-8+18,7-12)= (10,-5).
Then, B'=(10,-5)
For C(-11,12)
Under the translation rule (-11+18,12-12)=(7,0).
Then, C'(7.0)