Đáp án:
$\begin{array}{l}
1)\\
\frac{3}{{14}}:\frac{1}{{28}} - \frac{{13}}{{21}}:\frac{1}{{28}} + \frac{{29}}{{42}}:\frac{1}{{28}} - 6\\
= \left( {\frac{3}{{14}} - \frac{{13}}{{21}} + \frac{{29}}{{42}}} \right):\frac{1}{{28}} - 6\\
= \frac{{3.3 - 13.2 + 29}}{{42}}.28 - 6\\
= \frac{{12.28}}{{42}} - 6\\
= 8 - 6\\
= 2\\
2)\\
10.\left( {\frac{{\frac{1}{3} - \frac{1}{5} + \frac{1}{7}}}{{\frac{7}{3} - \frac{7}{5} + 1}} + \frac{{\frac{6}{5} + \frac{6}{{11}} - \frac{6}{{13}}}}{{\frac{7}{5} + \frac{7}{{11}} - \frac{7}{{13}}}}} \right):\frac{{686868}}{{343434}}\\
= 10.\left( {\frac{{\frac{1}{3} - \frac{1}{5} + \frac{1}{7}}}{{7\left( {\frac{1}{3} - \frac{1}{5} + \frac{1}{7}} \right)}} + \frac{{6.\left( {\frac{1}{5} + \frac{1}{{11}} - \frac{1}{{13}}} \right)}}{{7.\left( {\frac{1}{5} + \frac{1}{{11}} - \frac{1}{{13}}} \right)}}} \right):2\\
= 10.\left( {\frac{1}{7} + \frac{6}{7}} \right).\frac{1}{2}\\
= 10.\frac{7}{7}.\frac{1}{2}\\
= 5
\end{array}$
