Answer: (-6, 3)
Step-by-step explanation:
First step is to locate point C. It is at location (6, 3)
Reflecting this over the y axis will change the sign of the x coordinate, while keeping the y coordinate the same. We go from (6, 3) to (-6, 3)
The algebraic rule for this is

Therefore, point C' is located at (-6, 3)