xy/(x+y)=2
xy=2(x+y)
(3x-5xy+3y)/(-x+2xy-y)
=[3(x+y)-5xy]/[2xy-(x+y)]
=[3(x+y)-10(x+y)]/[4(x+y)-(x+y)]
=-7(x+y)/[3(x+y)]
=-7/3