6

The question requests the following:
Part I - a proof for
\begin{equation*}
\frac{a}{b}\times \frac{c}{d}=\frac{a\times c}{b\times d}
\end{equation*}
Part II - a proof for
\begin{equation*}
\frac{a}{b}\times \frac{c}{c}=\frac{a}{b}
\end{equation*}
Part III - a proof for
\begin{equation*}
\frac{a}...