5x-{2y-3x+[5x-2(y-2x)+3y]}
=5x-[2y-3x+(5x-2y+4x+3y)]
=5x-[2y-3x+(9x+y)]
=5x-(2y-3x+9x+y)
=5x-(3y+6x)
=5x-3y-6x
=-x-3y
=-(-1/2)-3*(-1/6)
=1/2+1/2
=1