答案1
使用{minipage}
:
\documentclass[leqno]{article}
\usepackage{lipsum}
\begin{document}
\lipsum[2]
%
\begin{equation}
\begin{minipage}{10cm}
If $F \subseteq E(G)$ is feasible on $V_j^1 \cup V_j^2 $,
then $d_F(x)$ is odd if $x \in V_j^1$ and $d_F(x)$ is even
if $x \in V_j^2$
\end{minipage}
\end{equation}
\end{document}