$a)\frac{15}{24}=\frac{15:3}{24:3}=\frac{5}{8}$

$b)\frac{35}{75}=\frac{35:5}{75:5}=\frac{7}{15}$ $b)\frac{35}{75}=\frac{35:5}{75:5}=\frac{7}{15}$

$c)2\frac{14}{21}=2\frac{14:7}{21:7}=2\frac{2}{3}$

$d)5\frac{36}{63}=5\frac{36:9}{63:9}=5\frac{4}{7}$

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

$f)12,25=12\frac{25}{100}=12\frac{1}{4}$