\(a+b=-4\); \(b+c=-6\); \(a+c=12\)
\(\Rightarrow a+b+b+c+a+c=\left(-4\right)+\left(-6\right)+12\)
\(\Rightarrow2\left(a+b+c\right)=2\)\(\Rightarrow a+b+c=1\)
\(a+b=-4\)\(\Rightarrow c=1-\left(-4\right)=5\)
\(b+c=-6\)\(\Rightarrow a=1-\left(-6\right)=7\)
\(a+c=12\)\(\Rightarrow b=1-12=-11\)
Vậy \(a=7\), \(b=-11\), \(c=5\)