①1/2(8x-6y)+3(y-x/3)
=4x-3y+3y-x
=(4x-x)+(-3y+3y)
=3x
②3(2x-3y)-2(3x-2y)
=6x-9y-6x+4y
=(6x-6x)+(-9y+4y)
=-5y
③2(x²-3xy)-3(y²-2xy)
=2x²-6xy-3y²+6xy
=2x²-3y²