To find the coordinates of the vertex \( X' \) after triangle \( XYZ \) is reflected over a horizontal line, we need to know the original coordinates of vertex \( X \) and the equation of the horizontal line of reflection.
Assuming the original coordinates of vertex \( X \) are \( (x, y) \) and the horizontal line of reflection is given by \( y = k \), the reflected coordinates \( X' \) will be given by the formula:
\[ X' = (x, 2k - y) \]
Without the original coordinates of vertex \( X \) or the specific horizontal line of reflection, we cannot determine the resulting coordinates for \( X' \).
If you provide the coordinates of vertex \( X \) and the equation of the horizontal line of reflection, I would be able to calculate the coordinates of \( X' \) for you.