参考：http://blog.sina.com.cn/s/blog_5e16f1770100nd48.html

\(
\begin{tabular}{lr}
&12\\
+&143\\
+&654\
+&24\\
\hline
=&\small$\square\!\square\!\square$
\end{tabular}
\)

然鹅报错：Unknown environment ‘tabular’