$\text{a)}\frac{\left(0,6+0,425-0,025\right):0,01}{\left(4\frac{5}{9}+6\frac{1}{9}\right)\cdot 6}=\frac{\left(0,6+0,4\right):0,01}{10\frac{6}{9}\cdot 6}=\frac{1:0,01}{10\frac{2}{3}\cdot 6}=\frac{100}{\frac{32}{{\sout{3}}^1}\cdot {\sout{6}}^2}=\frac{100}{64}=\frac{25}{16}$