Theorem numbering in LaTeX

Question

I have a problem with theorem numbering in LaTeX. I can make it number by subsection, e.g

Theorem 1.2.1

for the first theorem in

Answer 1

You can use this command for renew command section and subsection and theorem's and ...

\renewcommand{\theequation}{\thesection.\arabic{equation}}
\renewcommand{\thesection}{\arabic{section}}
\renewcommand{\thesubsection}{(\alph{subsection})}‎‎‎