原式=3X²Y-2XY²+2XY-3X²Y-XY+3XY²
=(3-3)X²Y+(3-2)XY²+(2-1)XY
=XY²+XY
=XY(Y+1)
∵X=3 Y=-1/3
∴原式=3×(-1/3)(-1/3+1)
=-1×2/3
=-2/3