a+2b=-3.①
b+3c=1.②
a-c=2.③

①-③,得
2b+c=-5
上式与②联立,得
2b+c=-5··········④
b+3c=1···········⑤
④-⑤×2,得
-5c=-7
c=7/5
将c=7/5代入⑤,得：b=-16/5,
将c=7/5代入③,得：a=17/5；
综上,得
a=17/5
b=-16/5
c=7/5