x+y=5 (1)y+z=7 (2)z+x=6 (3)(1+2+3)÷2得：x+y+z=9 (4)4-1 得：z=44-2得：x=24-3得：y=3
用z+x=6式减x+y=5式得z-y=1.用z-y=1式加y+z=7式得2z=8,即得z=4.易知y=3,x=2.
