Matrices And Determinants

If the co-factors of the elements 3, 7 and 6 of the matrix $\left[\begin{array}{ccc}1 & 2 & 3 \\ 4 & -1 & 7 \\ 2 & 4 & 6\end{array}\right]$ are $a, b$ and $c$ respectively, then $\left[\begin{array}{lll}a & b & c\end{array}\right]\left[\begin{array}{l}1 \\ 4 \\ 2\end{array}\right]+\left[\begin{array}{lll}a & b & c\end{array}\right]\left[\begin{array}{l}3 \\ 7 \\ 6\end{array}\right]=$