Đáp án:
\(\begin{array}{l}
a)\,\,\frac{8}{{27}}\\
b)\,\,\,\frac{7}{{19}}
\end{array}\)
Giải thích các bước giải:
\[\begin{array}{l}
a)\,\,\frac{3}{5} \times \frac{8}{{27}} \times \frac{5}{3} = \frac{{3 \times 8 \times 5}}{{5 \times 27 \times 3}} = \frac{8}{{27}}.\\
b)\,\,\frac{7}{{19}} \times \frac{1}{3} + \frac{7}{{19}} \times \frac{2}{3} = \frac{7}{{19}}\left( {\frac{1}{3} + \frac{2}{3}} \right) = \frac{7}{{19}}.
\end{array}\]
