\documentclass{article}

\usepackage{amsmath,amsfonts,graphicx}

%\renewcommand{\flhead}{Expert-Group Role}
%\renewcommand{\blhead}{Home-Group Role}
%Needed for my printer.
%\addtolength{\topmargin}{-0.3cm}
%\addtolength{\evensidemargin}{-1mm}

\begin{document}

Card 1:

$f(x) = 
            \begin{cases}
                x, & x < 0 \\
                0, & x \ge 0
            \end{cases}.$

\end{document}
