\[\boxed{\text{5.4}\text{3}\text{7.}}\]
\[\textbf{а)}\ \frac{40}{60} = \frac{2}{3} = \frac{24}{36}\text{\ \ }\]
\[\frac{22}{99} = \frac{2}{9} = \frac{8}{36}\ \]
\[\frac{66}{88} = \frac{3}{4} = \frac{27}{36}\ \]
\[\textbf{б)}\ \frac{21}{56} = \frac{3}{8} = \frac{18}{48}\ \]
\[\frac{10}{96} = \frac{5}{48}\ \]
\[\frac{200}{240} = \frac{20}{24} = \frac{5}{6} = \frac{40}{48}\text{\ \ }\]