Answer:
(-4,-6)
Step-by-step explanation:
If your point D were to start at (4,6), the first 90° clockwise rotation would have the point land on (4,-6), the second would have point D land on (-4,-6). A faster way to do this without making 2 90° clockwise rotations, is you flip it diagonally across the center point, if the center point is 0, you would flip both signs (positive would become negative and the other way around).