一种不需要太花哨包装的可能性。
\documentclass{article}
\usepackage{amsmath,tabularx}
\begin{document}
\begin{tabularx}{\linewidth}{|p{3cm}>{\centering}X}
\cline{1-1}
\emph{Solution}: & $\displaystyle\int\limits_0^6\pi\,f(y)\,\mathrm{d}y$
\end{tabularx}
\end{document}
![在此处输入图片描述](https://i.stack.imgur.com/x34YK.png)