\begin{exercise}
Solve: $\displaystyle\lim_{n\to\infty} \frac{2n}{3n+1}$
\begin{solution}
We have,
\[
  \lim_{n\to\infty} \frac{2n}{3n+1} = \frac{2}{3+\frac{1}{n}}=\fbox{$\displaystyle\frac23$}
\]
\end{solution}
\end{exercise}