$\frac{18}{20} = \frac{9 * 2}{10 * 2} = \frac{9}{10}$
$\frac{5}{10} = \frac{1 * 5}{2 * 5} = \frac{1}{2}$
$\frac{16}{12} = \frac{4 * 4}{3 * 4} = \frac{4}{3}$
$\frac{30}{20} = \frac{3 * 10}{2 * 10} = \frac{3}{2}$
$\frac{12}{9} = \frac{4 * 3}{3 * 3} = \frac{4}{3}$
$\frac{2}{6} = \frac{1 * 2}{3 * 2} = \frac{1}{3}$

$\frac{55}{22} = \frac{5 * 11}{2 * 11} = \frac{5}{2}$
$\frac{17}{51} = \frac{1 * 17}{3 * 17} = \frac{1}{3}$
$\frac{12}{8} = \frac{3 * 4}{2 * 4} = \frac{3}{2}$
$\frac{24}{40} = \frac{3 * 8}{5 * 8} = \frac{3}{5}$
$\frac{15}{6} = \frac{5 * 3}{2 * 3} = \frac{5}{2}$
$\frac{10}{100} = \frac{1 * 10}{10 * 10} = \frac{1}{10}$