x-y+z=9 (1)
2x+y+3z=10 (2)
3x+2y-4z=3 (3)
(1)+(2)
3x+4z=19 (4)
(1)×2+(2)
5x-2z=21 (5)
(4)+(5)×2
13x=61
x=61/13
z=(19-3x)/4=16/13
y=x+z-9=-40/13