已知x+2y+3z=21,3x+2y+z=19,求x+y+z的值.

已知x+2y+3z=21,3x+2y+z=19,求x+y+z的值.
已知x+2y+3z=21,3x+2y+z=19,求x+y+z的值.

已知x+2y+3z=21,3x+2y+z=19,求x+y+z的值.
2式减去1式为2x-2z=-2,即x=z-1,1式*3-2式为4y+8z=44,即y+2z=11,x+y+z=（z-1）+y+z=y+2z-1=11-1=10,即x+y+z=10