Section 6 Cross Reference 2

Chapter
\chapter{Authoring}\label{chap:abc}
Section
\section{Cross Reference 2}\label{sec:abc}
Equation
\begin{equation}\label{equ:abc}
    1 + 1 = 2
\end{equation}
\begin{equation}\tag{5.1} 1 + 1 = 2 \end{equation}
\[\tag{S}\label{equ:bcd}
    1 + 1 = 3
\]
\[\tag{S}\label{equ:bcd} 1 + 1 = 3 \]