$a)\frac{1}{5}=\frac{20}{100}>\frac{1}{100}$
$⇒\frac{1}{5}>\frac{1}{100}$
$b)\frac{3}{10}=\frac{18}{60}$
$\frac{17}{12}=\frac{85}{60}$
$Ta thấy:\frac{18}{60}<\frac{85}{60}$
$⇒\frac{3}{10}<\frac{17}{12}$
$c)\frac{8}{-7}=\frac{-104}{91}$
$\frac{-9}{13}=\frac{-63}{91}$
$Ta thấy:\frac{-104}{91}<\frac{-63}{91}$
$⇒\frac{8}{-7}<\frac{-9}{13}$