For reflection on the x-axis, you negate the all y coordinate
a) coordinate of R A'B'C' after reflection on x-axis is (-5, -6) , (-3, 4) and (1, 2)
For reflection on the y-axis, you negate the all x coordinate
b) coordinate of R A'B'C' after reflection on x-axis is (5, 6) , (3, -4) and (-1, -2)