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.
If You know how to do long division then... You move the decimal that’s outside the house to where it’s not there no more then divide . Or turn the decimals into Fractions and do the reciprocal.