\documentclass[12pt]{article}

\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{pst-plot}
\usepackage{color}
\pagestyle{empty}

\begin{document}
\[
\bar{D}\left(G\right)
    = \frac
        {\displaystyle\sum_{u \in V}{\bar{D}\left(u\right)}}
        {\left(\left|V\right|\right)}
    = \frac
        {\displaystyle\sum_{u \in V}\sum_{v \in V}{d\left(u,v\right)}}
        {\left|V\right| \cdot \left(\left|V\right|-1\right)}
\]
\end{document}