\left[ {\begin{array}{*{20}c}
 {\rm 3} & {{\rm 913}} \\
 {{\rm 913}} & {{\rm 278249}} \\
\end{array}} \right]\left[ {\begin{array}{*{20}c}
 b \\
 a \\
\end{array}} \right] = \left[ {\begin{array}{*{20}c}
 {311} \\
 {94780} \\
\end{array}} \right]