(x-3xy-y)/(3x-2xy-3y)
={xy[(1/y)-3-(1/x)]}/{xy[(3/y)-2-(3/x)]}
=[(1/y)-(1/x)-3]/[(3/y)-(3/x)-2]
=[(-3)-3]/[3*(-3)-2]
=(-6)/(-9-2)
=(-6)/(-11)
=6/11