Given the cordinates of the vertices of a triangle :
A(6,6), B(12,9), C(9,6).
A reflection across the x-axis implies that the x-cordinates of the vertices remain the same, while the y-cordinates take negative values.
The new cordinates of the vertices after reflection :
A(6, -6), B(12, -9), C(9, -6)