To reflect a point over the y-axis, you change the sign of the x-coordinate while keeping the y-coordinate the same.
Point D is originally at the coordinates \( (5, 6) \).
To reflect point D over the y-axis:
- Change the x-coordinate from 5 to -5.
- The y-coordinate remains 6.
Therefore, the coordinates of point D after reflection over the y-axis are \( (-5, 6) \).
Final answer: \((-5, 6)\)