Answer:
P'(-x,y)
Explanation:
The question is asking you to reflect over the y-axis. You pick a random point in the first quadrant and reflect that point over the y-axis. The point will land in the second quadrant and the x-value will have been negated (changed sign).
Ex.
(5,4) would become (-5,4)
P(x,y) reflected over the y-axis P'(-x,y)