\documentclass{standalone}
\begin{filecontents*}{\jobname.txt}
a b c
1  2 2.0
2  4 2.5
3  6 3.0
4  8 3.5
5 10 4.0
\end{filecontents*}
\usepackage{pgfplots}
\begin{document}

\begin{tikzpicture}
  \begin{axis}
   \addplot[only marks]
     table[y expr = \thisrow{b}/\thisrow{c}] {\jobname.txt};
  \end{axis}
\end{tikzpicture}

\end{document}

\documentclass{standalone}
\begin{filecontents*}{\jobname.txt}
a b c
1  2 2.0
2  4 2.5
3  6 3.0
4  8 3.5
5 10 4.0
\end{filecontents*}
\usepackage{pgfplots}
\begin{document}

\begin{tikzpicture}
  \begin{axis}
   \addplot[only marks]
     table[y expr = 100 * \thisrow{b}/\thisrow{c}] {\jobname.txt};
  \end{axis}
\end{tikzpicture}

\end{document}

\documentclass{standalone}
\begin{filecontents*}{\jobname.txt}
a b c
1  2 2.0
2  4 2.5
5  6 3.0
10  8 3.5
20 10 4.0
\end{filecontents*}
\usepackage{pgfplots}
\begin{document}

\begin{tikzpicture}
  \begin{axis}[xmode = log]
   \addplot[only marks]
     table[y expr = 100 * \thisrow{b}/\thisrow{c}] {\jobname.txt};
  \end{axis}
\end{tikzpicture}

\end{document}

Oh, and if you forget to enable Track changes, then your changes are completely lost. This is because Word tracks actual changes rather than comparing two versions like a sane version system like Git would do.