(x+3y-3xy)-2(xy-2x-y)
=X+3Y-3XY-2XY+4X+2Y
=5X+5Y-5XY
=5(X+Y)-5XY,
∵X+Y=1/3,XY=-1/2,
∴原式=5×1/3-5×(-1/2)
=5/3+5/2
=25/6.