Answers:
B ' (6, 4)
C ' (2, 3)
D ' (3, -1)
E ' (7, 0)
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Step-by-step explanation:
The y-axis reflection rule is:

The x coordinate flips from positive to negative, or vice versa. The y coordinate stays the same.
So for example, the point B(-6,4) moves to B ' (6, 4).
You can use a graphing tool like GeoGebra to confirm the answers are correct.