г) \(\frac{1}{9}(0,9b - 1,8) - \frac{1}{2}(0,2b - 0,4)\).

\[\frac{1}{9}(0.9b - 1.8) - \frac{1}{2}(0.2b - 0.4)\]

\[= \frac{1}{9} \cdot 0.9b - \frac{1}{9} \cdot 1.8 - \frac{1}{2} \cdot 0.2b + \frac{1}{2} \cdot 0.4\]

\[= \frac{9}{90}b - \frac{18}{90} - \frac{2}{20}b + \frac{4}{20}\]

\[= \frac{1}{10}b - \frac{1}{5} - \frac{1}{10}b + \frac{1}{5} = 0\]

Ответ: 0