\(\frac{6}{7}-\frac{5}{21}+\left[3\frac{1}{3}-4\frac{1}{14}\right]=x-\left[\frac{1}{2}-\left|-\frac{1}{3}\right|\right]\)
\(\Leftrightarrow\frac{18}{21}-\frac{5}{21}+\left[\frac{10}{3}-\frac{57}{14}\right]=x-\left[\frac{1}{2}-\frac{1}{3}\right]\)
\(\Leftrightarrow\frac{13}{21}+\left[-\frac{31}{42}\right]=x-\frac{1}{6}\)
\(\Leftrightarrow-\frac{5}{42}=x-\frac{1}{6}\Leftrightarrow-\frac{5}{42}-x=-\frac{1}{6}\)
\(\Leftrightarrow x=-\frac{5}{42}-\left[-\frac{1}{6}\right]=\frac{1}{21}\)