\documentclass[11pt,dvips]{article}
\begin{document}

\begin{LARGE}

$$
\begin{array}{rcr}
2 v_A + v_B - 3 v_C & = & 7 \\
-2 v_A + 6 v_B & = & 0 \\
-3 v_B + 3 v_A & = & -6
\end{array}
$$
\end{LARGE}

\end{document}
