2. Calculate: $\frac{2 \times 4.6 \times 9+4 \times 9.2 \times 18}{1 \times 2.3 \times 4.5+3 \times 6.9 \times 13.5}=$ $\qquad$
$$
\begin{array}{l}
\text { [Solution] Solution: } \frac{2 \times 4.6 \times 9+4 \times 9.2 \times 18}{1 \times 2.3 \times 4.5+3 \times 6.9 \times 13.5} \\
=\frac{1 \times 2 \times 2.3 \times 2 \times 4.5 \times 2+1 \times 4 \times 2.3 \times 4 \times 4.5 \times 1}{1 \times 2.3 \times 4.5+1 \times 3 \times 2.3 \times 3 \times 4.5 \times 3} \\
=\frac{8 \times 1 \times 2.3 \times 4.5+64 \times 1 \times 2.3 \times 4.5}{1 \times 2.3 \times 4.5+27 \times 1 \times 2.3 \times 4.5} \\
=\frac{72 \times 1 \times 2.3 \times 4.5}{28 \times 1 \times 2.3 \times 4.5} \\
=\frac{72}{28} \\
=\frac{18}{7} .
\end{array}
$$

Therefore, the answer is: $\frac{18}{7}$.