\[18,65 \approx 18,7\]
\[\mathrm{\Delta}x = |a - x| = |18,7 - 18,65| = 0,05.\]
\[\delta x = \frac{\mathrm{\Delta}x}{a} = \frac{0,05}{18,7} =\]
\[= \frac{5}{1870} = \frac{1}{374} \approx 0,003.\]