3/5*7/9-3/5*(7/9-5/6)
[m]\frac{3}{5}\cdot \frac{7}{9}–\frac{3}{5}\cdot (\frac{7}{9}–\frac{5}{6})=\frac{3}{5}\cdot \frac{7}{9}-\frac{3}{5}\cdot \frac{7}{9}+\frac{3}{5}\cdot\frac{5}{6}=\frac{3}{5}\cdot\frac{5}{6}=\frac{3}{6}=\frac{1}{2}[/m]