I have a problem with the following code.
\begin{subequations}
\begin{empheq}{align}
& a = b \label{E1} \\
& c = d \label{E2}
\end{empheq}
\end{subequations}
\begin{subequations}
\begin{empheq}{align}
& \alpha = \beta \tag{\ref{E1}$^\prime$} \label{G1} \\
& \gamma = \delta \tag{\ref{E2}$^\prime$} \label{G2}
\end{empheq}
\end{subequations}
\begin{equation}
F(a,c) = 0 \label{E3}
\end{equation}
My problem concerns the equation {E3} since I obtain the sequence of equations tags (1a), (1b), (1a'), (1b') and (3) but i would like to have a tag like (2) on the last equation line. I tried to change the equation counter but I have no results.
I thank you for your help