为多行“方程”编号

Question

我正在尝试对一个跨越多行的方程进行编号。我需要它看起来像这样

我当前的文本如下：

\documentclass[a4paper,12pt]{article}

\begin{center}
 {\it ``If A is true, then B is true\\
  A is true \\ 
  \line(1,0){140}
  \\Therefore, B is true''}
\end{center}

Answer 1

\documentclass[a4paper,12pt]{article}
\begin{document}
\begin{equation}
 \begin{tabular}{c}
  ``If  $A$ is true, then $B$ is true\\
  $A$ is true \\\hline
  Therefore, $B$ is true''
  \end{tabular}
\end{equation}
\end{document}