x+y-2z=5 (1) 2x-y-z=4 (2) 3x+y-3z=10 (3) (1)+(2) 3x-3z=9 x-z=3 (4) (2)+(3) 5x-4z=14 (5) (5)-(4)×4 5x-4x=14-12 所以 x=2 z=x-3=-1 y=5+2z-x=1
