Modify numbering style of subequations

Question

the following MWE produces a subequation numbering of 1a and 1b. However, I would like to have it displayed as 1A and 1B. I probably have to rename, \theequation, but so far I did not have any success :(. Do you know the correct code?

Thank you

\documentclass{report}
\usepackage{amsmath}
\begin{document}
\begin{subequations}
\begin{align} 
3 &= 1+2 \\
6 &= 2+4 
\end{align}
\end{subequations}
\end{document}

Answer 1

You can patch the subequations environment with etoolbox's \patchcmd to use \Alph instead of \alph:

\documentclass{report}
\usepackage{amsmath}
\usepackage{etoolbox}
\patchcmd\subequations{\alph}{\Alph}{}{\GenericError{}{Patching failed.}{}{}}
\begin{document}
\begin{subequations}
\begin{align} 
3 &= 1+2 \\
6 &= 2+4 
\end{align}
\end{subequations}
\end{document}

EDIT: If hyperref is already loaded, instead of patching subequations we have to patch HyOrg@subequations. The following does so (without testing whether hyperref is actually loaded):

\documentclass{report}
\usepackage{amsmath}
\usepackage{etoolbox}
\usepackage[]{hyperref}
\makeatletter
\AtBeginDocument
  {%
    \patchcmd\HyOrg@subequations
      {\alph}{\Alph}{}{\GenericError{}{Patching failed}{}{}}%
  }
\makeatother
\begin{document}
\begin{subequations}
\begin{align} 
3 &= 1+2 \\
6 &= 2+4 
\end{align}
\end{subequations}
\end{document}

EDIT2: If you can control when hyperref is loaded, you can simply do the patching of the first code in this answer, and load hyperref afterwards. hyperref uses the definition in effect when it was loaded.