Please explain as well how to do it. Thanks!

Answer:
The answer is B.
Step-by-step explanation:
Please refer to the attachment (ignore the horrible drawing, thank you).
Let the distance from P to T be red. The length of the red distance is x radians.
T’ is π-x. Thus, it is the red distance subtracted from the purple distance.
So, T’ is the reflection of T across the y-axis.
Therefore, we can simply multiply the x-coordinate of T to get T’.
T is (3/5, 4/5)
Then T’ must be (-3/5, 4/5).
Hence, our answer is B.