# How to use \tag{} for multiple equation in align*

I am working on a report. One of that is to requote many equations from paper. I often use:

\begin{align*}\tag{5}
x = a + b
\end{align*}


This works fine for a single equation. However, is there any way to tag many equations in a single \align*, instead of working manually like:

\begin{align*}\tag{5}
x = a + b
\end{align*}
\begin{align*}\tag{10}
y = c + d
\end{align*}


Thank you

First and foremost: don't use align for single equations.

Second: align is for multiline displays.

\begin{align}
x &= a+b \tag{*} \\
y &= c+d \tag{**}
\end{align}


You say you have to repeat equations. Then you shouldn't use an explicit number.

%%% in section 1
$$\label{important} x=a+b$$

%%% in section 3
$$\tag{\ref{important}} x=a+b$$


The same with align.