$a)\frac{9}{10}=0,9$

$b)\frac{7}{25}=\frac{28}{100}=0,28$

$c)\frac{47}{4}=11\frac{3}{4}=11\frac{75}{100}=11,75$

$d)\frac{31}{20}=1\frac{11}{20}=1\frac{55}{100}=1,55$