Đáp án:
$\begin{array}{l}
\frac{{16}}{7}:\frac{2}{3}.x = \frac{5}{{28}}\\
\Rightarrow \frac{{16}}{7}.\frac{3}{2}.x = \frac{5}{{28}}\\
\Rightarrow \frac{{24}}{7}.x = \frac{5}{{28}}\\
\Rightarrow x = \frac{5}{{28}}.\frac{7}{{24}}\\
\Rightarrow x = \frac{5}{{96}}\\
\frac{{13}}{{31}}.x + \frac{7}{{18}} = \frac{{35}}{{27}}\\
\Rightarrow \frac{{13}}{{31}}.x = \frac{{35}}{{27}} - \frac{7}{{18}}\\
\Rightarrow \frac{{13}}{{31}}.x = \frac{{35.2 - 7.3}}{{54}}\\
\Rightarrow \frac{{13}}{{31}}.x = \frac{{49}}{{54}}\\
\Rightarrow x = \frac{{49}}{{54}}.\frac{{31}}{{13}}\\
\Rightarrow x = \frac{{1519}}{{702}}
\end{array}$
