$\text{a)}$

$0,2=\frac{2}{10}=\frac{1}{5}$

$0,5=\frac{5}{10}=\frac{1}{2}$  

$0,6=\frac{6}{10}=\frac{3}{5}$  

 

$\text{b)}$

$0,25=\frac{25}{100}=\frac{1}{4}$  

$0,50=\frac{50}{100}=\frac{1}{2}$  

$0,75=\frac{75}{100}=\frac{3}{4}$  

 

$\text{c)}$

$0,125=\frac{125}{1000}=\frac{1}{8}$

$0,375=\frac{375}{1000}=\frac{3}{8}$

$0,075=\frac{75}{1000}=\frac{3}{40}$