\[\left| \frac{1}{7} - 0,14 \right| = \left| \frac{1}{7} - \frac{7}{50} \right| = \left| \frac{50}{350} - \frac{49}{350} \right| = \frac{1}{350}.\]
\[Ответ:\ \frac{1}{350}.\]