$$\underset{\,\,\,\,{\textcolor[rgb]{0.66,0.66,0.66}{\rightarrow {\mathtt{u1, r, u2, x}}}}}{{solve}}{\left(\begin{array}{l}{\mathtt{u1}}={\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{\pi}}{\mathtt{\,\times\,}}{\mathtt{r}}\\
{\mathtt{u2}}={\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{\pi}}{\mathtt{\,\times\,}}\left({\mathtt{r}}{\mathtt{\,\small\textbf+\,}}{\mathtt{x}}\right)\\
{\mathtt{u2}}={\mathtt{u1}}{\mathtt{\,\small\textbf+\,}}{\mathtt{1}}\end{array}\right)} \Rightarrow \left\{ \begin{array}{l}{\mathtt{u1}} = {\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{r2}}{\mathtt{\,\times\,}}{\mathtt{\pi}}\\
{\mathtt{r}} = {\mathtt{r2}}\\
{\mathtt{u2}} = {\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{r2}}{\mathtt{\,\times\,}}{\mathtt{\pi}}{\mathtt{\,\small\textbf+\,}}{\mathtt{1}}\\
{\mathtt{x}} = {\frac{{\mathtt{1}}}{\left({\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{\pi}}\right)}}\\
\end{array} \right\}$$
x=1/(2*pi) = ca. 16cm