Calculer:
\begin{enumerate}
\begin{multicols}{4}
\item $\left|\dfrac{1}{2}-\dfrac{1}{3}\right|$
\item $\left|\dfrac{1}{5}-\dfrac{1}{3}\right|$
\item $\left|\dfrac{2}{7}-\dfrac{7}{2}\right|$
\item $\left|\dfrac{2}{3}-\dfrac{2}{5}\right|$
\end{multicols}
\end{enumerate}

