Đáp án:
$\begin{array}{l}
34)\left( {\frac{2}{{11}} + \frac{1}{3}} \right).x = \left( {\frac{1}{7} - \frac{1}{8}} \right).56\\
\frac{{6 + 11}}{{33}}.x = \frac{{8 - 7}}{{56}}.56\\
\frac{{17}}{{33}}.x = 1\\
x = \frac{{33}}{{17}}\\
Vậy\,x = \frac{{33}}{{17}}\\
36)x:\left( { - \frac{1}{6}} \right) = \frac{{13}}{{ - 19}} + \frac{8}{{15}}\\
\Rightarrow x:\left( { - \frac{1}{6}} \right) = \frac{{ - 13.15 + 8.19}}{{19.15}}\\
\Rightarrow x:\left( { - \frac{1}{6}} \right) = \frac{{ - 43}}{{285}}\\
\Rightarrow x = \frac{{ - 43}}{{285}}.\left( { - \frac{1}{6}} \right)\\
\Rightarrow x = \frac{{43}}{{1710}}\\
40)\frac{3}{5}x - \frac{1}{5} = \frac{9}{5}\\
\Rightarrow 3x - 1 = 9\\
\Rightarrow 3x = 10\\
\Rightarrow x = \frac{{10}}{3}\\
42)\frac{5}{8}.x + \frac{2}{5} = \frac{1}{5}\\
\Rightarrow \frac{5}{8}x = \frac{1}{5} - \frac{2}{5} = - \frac{1}{5}\\
\Rightarrow x = \frac{{ - 1}}{5}:\frac{5}{8}\\
\Rightarrow x = - \frac{8}{{25}}\\
44)\frac{{13}}{{15}} - \left( {\frac{{13}}{{21}} + x} \right).\frac{7}{{21}} = \frac{7}{{10}}\\
\Rightarrow \left( {\frac{{13}}{{21}} + x} \right).\frac{1}{3} = \frac{{13}}{{15}} - \frac{7}{{10}} = \frac{1}{6}\\
\Rightarrow \frac{{13}}{{21}} + x = \frac{1}{6}:\frac{1}{3} = \frac{1}{2}\\
\Rightarrow x = \frac{1}{2} - \frac{{13}}{{21}} = - \frac{5}{{42}}
\end{array}$
Vậy $x = - \frac{5}{{42}}$
