Ответ:

а) \(\frac{4}{5}:\frac{3}{10}+\frac{1}{9}=\frac{4}{5}\cdot\frac{10}{3}+\frac{1}{9}=\frac{8}{3}+\frac{1}{9}=\frac{25}{9}=2\frac{7}{9}\).

б) \(\frac{4}{15}+\frac{3}{8}:\frac{5}{16}=\frac{4}{15}+\frac{3}{8}\cdot\frac{16}{5}=\frac{4}{15}+\frac{6}{5}=\frac{22}{15}=1\frac{7}{15}\).

в) \(1\frac{1}{2}-\frac{1}{6}:\frac{4}{21}=\frac{3}{2}-\frac{1}{6}\cdot\frac{21}{4}=\frac{3}{2}-\frac{7}{8}=\frac{5}{8}\).

г) \(2\frac{1}{4}:\frac{15}{16}-\frac{1}{4}=\frac{9}{4}\cdot\frac{16}{15}-\frac{1}{4}=\frac{12}{5}-\frac{1}{4}=\frac{43}{20}=2\frac{3}{20}\).

Ответ: а) \(2\frac{7}{9}\); б) \(1\frac{7}{15}\); в) \(\frac{5}{8}\); г) \(2\frac{3}{20}\).