x-2y=-9 (1)
y-z=3 (2)
2z+x=47 (3)
由（2）得,y=z+3 (4)
把(4)代入(1)
x-2z-6=-9 x-2z=-3 (5)
(3)+(5)
2x=44
x=22
z=25/2
y=31/2