\[2a^{2}b^{3} = 9 \Longrightarrow a^{2}b^{3} = \frac{9}{2} = 4,5:\]
\[2a^{4}b^{6} = 2 \cdot \left( a^{2}b^{3} \right)^{2} = 2 \cdot {4,5}^{2} =\]
\[= 2 \cdot \left( \frac{9}{2} \right)^{2} = 2 \cdot \frac{81}{4} = \frac{81}{2} = 40,5\]