Ответ:

  1. а) \(\frac{3}{8}:\frac{5}{16}=\frac{6}{5}\).
    \(\frac{4}{15}+\frac{6}{5}=\frac{4}{15}+\frac{18}{15}=\frac{22}{15}=1\frac{7}{15}\).
  2. б) \(\frac{1}{6}:\frac{4}{21}=\frac{7}{8}\).
    \(1\frac{1}{2}-\frac{7}{8}=\frac{5}{8}\).
  3. в) \(2\frac{1}{4}:\frac{15}{16}=\frac{9}{4}\cdot\frac{16}{15}=\frac{12}{5}\).
    \(\frac{12}{5}-\frac{1}{4}=\frac{43}{20}=2\frac{3}{20}\).

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