$\frac{2}{3} = \frac{24}{36}$,
$\frac{7}{9} = \frac{28}{36}$,
$\frac{9}{12} = \frac{27}{36}$.
Ответ: $\frac{7}{9} > \frac{9}{12} > \frac{2}{3}$

$-\frac{1}{6} = -\frac{6}{36}$,
$-\frac{2}{9} = -\frac{8}{36}$,
$-\frac{5}{12} = -\frac{15}{36}$.
Ответ: $-\frac{1}{6} > -\frac{2}{9} > -\frac{5}{12}$

$-\frac{1}{2} = -\frac{6}{12}$,
$-\frac{3}{4} = -\frac{9}{12}$,
$-\frac{7}{12}$.
Ответ: $-\frac{1}{2} > -\frac{7}{12} > -\frac{3}{4}$

$-\frac{7}{8} = -\frac{21}{24}$,
$-\frac{3}{4} = -\frac{18}{24}$,
$-\frac{5}{6} = -\frac{20}{24}$.
Ответ: $-\frac{3}{4} > -\frac{5}{6} > -\frac{7}{8}$

$\frac{3}{10} = \frac{15}{50}$,
$\frac{2}{5} = \frac{20}{50}$,
$\frac{9}{25} = \frac{18}{50}$.
Ответ: $\frac{2}{5} > \frac{9}{25} > \frac{3}{10}$

$\frac{21}{25} = \frac{42}{50}$,
$\frac{7}{10} = \frac{35}{50}$,
$\frac{4}{5} = \frac{40}{50}$.
Ответ: $\frac{21}{25} > \frac{4}{5} > \frac{7}{10}$