Вычислите: a) $$ \frac{4}{9} * (-\frac{3}{8}) $$ б) $$ \frac{5}{6} - \frac{4}{9} : \frac{16}{21} $$

a) $$ \frac{4}{9} * (-\frac{3}{8}) = -\frac{4*3}{9*8} = -\frac{12}{72} = -\frac{1}{6} $$

б) $$ \frac{5}{6} - \frac{4}{9} : \frac{16}{21} = \frac{5}{6} - \frac{4}{9} * \frac{21}{16} = \frac{5}{6} - \frac{4*21}{9*16} = \frac{5}{6} - \frac{84}{144} = \frac{5}{6} - \frac{7}{12} = \frac{10}{12} - \frac{7}{12} = \frac{3}{12} = \frac{1}{4} $$

Ответ: a) $$\frac{-1}{6}$$; б) $$\frac{1}{4}$$