The linear equation for two point in plan is: (x-a)/((y-b) =(x-c)/(y-d) where: a and b are the coordinates of the first point c and d are the coordinates of the second point (r-2)/(y-3) = (r-4)/(y-6) (r-2)(y-6)=(r-4)(y-3) -2y=-3r+12-4y Therefore the equation is: Y=3r/2
