The equation of the reflected ray is y+x = 6. Since based on the equation of the original ray is y-x=4 and the equation of the normal line y=5, the point where the normal line, the original ray and the reflected ray intersect is at point (1,5). By definition, substituting the normal line (y=5) and the point (1,5) to the given equations, y+x=6 satisfies the equality and therefore is the equation of the reflected ray
