x+y-z=4 .(1)
2x-y+3z=-3 .(2)
3x-y-2z=3 .(3)
(1)+(2) 3x+2z=1.(4)
(3)-(2) x-5z=6 .(5)
(4)-3X(5) 17z=-17
z=-1.(6)
(6)代入(5) x=1.(7)
(6)(7)代入(1) y=2