This is LaTeX code:
[latex]
\begin{pmatrix} a_{1,1} & a_{1,2} \\ a_{2,1} & a_{2,2} \\ a_{3,1} & a_{3,2} \end{pmatrix} \cdot \begin{pmatrix} 2\\ 1 \end{pmatrix} = \begin{pmatrix} 3\\ 1\\ 1 \end{pmatrix}
[/latex]