(4x-2y)-[5x-(8y-2x-x-y)]+x
=(4x-2y)-5x+(8y-2x-x-y)+x
=4x-2y-4x-(8y-2x-x-y)
=-2y-(8y-2x-x-y)
=-2y-7y+3x
=-9y+3x
=-3（3y-x）