$\frac{\left(0,02\cdot {10}^8\right)\cdot \left(3\cdot {10}^{-6}\right)}{0,6\cdot {10}^{10}}=\frac{0,06\cdot {10}^2}{0,6\cdot {10}^{10}}=0,1\cdot {10}^{-8}=\underset{0,1}{\underbrace{1\cdot {10}^{-1}}}\cdot {10}^{-8}=1\cdot {10}^{-9}$