$a)$

$0,4=\frac{4}{10}=\frac{2}{5}$

$0,08=\frac{8}{100}=\frac{4}{50}=\frac{2}{25}$

$0,15=\frac{15}{100}=\frac{3}{20}$

$1,375=1\frac{375}{1000}=1\frac{375:125}{1000:125}=1\frac{3}{8}$

$14,35=14\frac{35}{100}=14\frac{7}{20}$

$0,84=\frac{84}{100}=\frac{42}{50}=\frac{21}{25}$

 

 

$b)$

$\frac{3}{4}=\frac{75}{100}=0,75$

$\frac{5}{8}=\frac{5\cdot 125}{8\cdot 125}=\frac{625}{1000}=0,625$

$3\frac{1}{2}=3\frac{5}{10}=3,5$

$4\frac{2}{5}=4\frac{4}{10}=4,4$

$1\frac{9}{20}=1\frac{45}{100}=1,45$

$\frac{11}{25}=\frac{44}{100}=0,44$