),$$\documentclass[00pt]{minimal}                 \usepackage{amsmath}                 \usepackage{wasysym}                  \usepackage{amsfonts}                  \usepackage{amssymb}                  \usepackage{amsbsy}                 \usepackage{mathrsfs}                 \usepackage{upgreek}                 \setlength{\oddsidemargin}{-00pt}                 \begin{document}$$ \left\{ \begin{gathered} \frac{{{\text{d}}B}}{{{\text{d}}t}} = D_{R} \pi_{C} (C) - k_{B} B \hfill \\ \frac{{{\text{d}}C}}{{{\text{d}}t}} = D_{C} \frac{\alpha B}{0 + \beta R} - D_{A} \pi_{C} (C)C \hfill \\ \end{gathered} \right., $$\end{document}$$