解:?$(1)A+B=A-B+2B$?
?$=6x^2y+12xy-2x-9+2(3x^2y-5xy+x+7)$?
?$=6x^2y+12xy-2x-9+6x^2y-10xy+2x+14$?
?$=12x^2y+2xy+5$?
?$(2)$?即?$A-3B=A-B-2B$?
?$=6x^2y+12xy-2x-9-2(3x^2y-5xy+x+7)$?
?$=6x^2y+12xy-2x-9-6x^2y+10xy-2x-14$?
?$=22xy-4x-23$?
?$=(22y-4)x-23$?的取值與?$x$?無關(guān)
∴?$22y-4=0$?,得?$y=\frac {2}{11}$?