x+2y-z=6 ①
2x+y+z=9 ②
3x+4y+2z=19 ③
①×2-②
3y-3z=3
化简
y-z=1 ④
①×3-③
2y-5z=9 ⑤
④×2-⑤
3z=7
z=7/3
带入④
y=10/3
带入②
x=5/3
x=5/3
y=10/3
z=7/3