\begin{equation}
    \begin{tikzpicture}[scale=0.67, baseline={([yshift=-1pt]current bounding box.north)}]
        % axis, arrow style to-to
        \draw[{To[scale=1.3]}-{To[scale=1.3]}, line width=1pt] (-0.4, 0) -- (20.4, 0);
        % tick marks
        \foreach \x in {0,1,...,20}
            \draw[shift={(\x,0)},color=black, line width=1pt] (0pt,-14pt) -- (0pt,0pt);
        % numbers along each axis
        \foreach \x in {0,10,20}
            \draw[shift={(\x,-0.8)},color=black] node[font=\large,text height=12pt] {$\x$};
        % equation at right end
        \node [font=\large, anchor=east] at (25,1.65) {$  $};
    \end{tikzpicture}
\end{equation}