此类提的解法,3x+7y+z=5,3(x+y+z)+2(2y-z)=5
4x+10y+z=3,4(x+y+z)+3(2y-z)=3
另x+y+z=a,2y-z=b,则3a+2b=5,4a+3b=3,a=9,b=-11,
得x+y+z=9