LaTeX Forum

\documentclass{scrartcl}
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\usepackage[ngerman]{babel}
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\begin{document}

\begin{enumerate}[label={\alph*)}]


\item 
$\displaystyle \left\lbrace x \in \mathbb{R} \; |\; x-\lfloor x \rfloor = \operatorname{sign} (x) \right\rbrace$


\item
$\displaystyle \left\lbrace x \in \mathbb{R} \; |\; |x-1|+|2x+1| >5 \right\rbrace$


\item
$\left\lbrace \sin(x)+\cos(x)\leq \frac{2}{5} \right\rbrace$

\item
$\displaystyle \left\lbrace x \in \mathbb{R} \; \vert \; \left( \frac{x+4}{x-2} \right)^2 <x \right\rbrace$


\end{enumerate}
\end{document}

 $\displaystyle \left\lbrace x \in \mathbb{R} \; \middle\vert \; \left( \frac{x+4}{x-2} \right)^2 <x \right\rbrace$