When dealing with reflections over the x-axis, the only thing that we need to do is to negate the y-coordinate of the original figure.
The rule is: f(x, y) → f(x, -y).
Original Figure → Translated Figure
J (1, 4) → J' (1, -4)
A (3, 5) → A' (3, -5)
G (2, 1) → G' (2, -1)
Here is how it looks like when plotted. (Green is the original figure and Blue is the reflected figure)