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{\bf Theorem.} {\it Let $x\in {\mathbb R} $. Then
$$
 x + x    =   2x   \, .  %Comment
$$
}

{\it Proof:} Consider an equality
\begin{equation}
\label{eqn1kk}
1+1=2
\end{equation}
Can you multiply the equation (\ref{eqn1kk}) by $x$? 


\setcounter{equation}5

{\it Another proof\/}: Consider an equality
\begin{equation}
\label{eqn2kk}
1+1=2
\end{equation}
Can you multiply the equation (\ref{eqn2kk}) by $x$? 


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