\[x = \frac{3}{26};\ \ \ \ \ \ \ \ \ a = \frac{1}{9}\]
\[\mathrm{\Delta}x = \left| \frac{1}{9} - \frac{3}{26} \right| = \left| \frac{26 - 27}{234} \right| =\]
\[= \left| - \frac{1}{234} \right| = \frac{1}{234}\]