Đáp án:
$\begin{array}{l}
B = \frac{{2.4.10 + 4.6.8 + 14.16.20}}{{3.6.15 + 6.9.12 + 21.24.30}}\\
= \frac{{{2^3}.\left( {1.2.5 + 2.3.4 + 7.8.10} \right)}}{{{3^3}.\left( {1.2.5 + 2.3.4 + 7.8.10} \right)}}\\
= \frac{{{2^3}}}{{{3^3}}} = \frac{8}{{27}}
\end{array}$