-(-3x-y+2z)-{-x+【4x-(x-y-z)-3x+2z}
=3x+y-2z+x-【4x-(x-y-z)]+3x-2z
=7x+y-4z-4x+(x-y-z)
=3x+y-4z+x-y-z
=4x-5z