We do not know the coordinates of triangle ABC, however, if the coordinates were (hypothetially) A (-2,0) B (-2,2) and C (-1,0) then we would flip triangle ABC over the line x=-3, point A would move 2 points horizontally to the left. Point B would move 2 points horizontally to the left. Point C, would move 4 points horizontally to the left. The Y coordinates would stay the same. Basically, instead of flipping it over the origin, you "move the origin" to whichever point you are told, they would function the same.
