Answer:
90 degrees clockwise rotation
Explanation:
The way to do this is by looking at your transformation rules, where you will find that in a 90 degree clockwise rotation you take your original X and Y, swap them, and make Y negative (y, -x).
To find this, pick any two points from each rectangle (Each point must have the same letter) and compare them:
Example:
Q is at (4, 2) and Q' is at (2,-4). When comparing the two points you will find that X and Y have been swapped, and Y is now negative. This matches the 90 degree clockwise rotation rule