\[\left| \frac{3}{7} - 0,43 \right| = \left| \frac{3}{7} - \frac{43}{100} \right| = \left| \frac{300}{700} - \frac{301}{700} \right| =\]
\[= \left| - \frac{1}{700} \right| = \frac{1}{700}\]
\[Ответ:\ \frac{1}{700}.\]