\[x = \frac{1}{6};\ \ \ \ \ \ \ a = 0,2\ \]
\[\mathrm{\Delta}x = \left| 0,2 - \frac{1}{6} \right| = \left| \frac{1}{5} - \frac{1}{6} \right| =\]
\[= \left| \frac{6 - 5}{30} \right| = \left| \frac{1}{30} \right| = \frac{1}{30}\]