Найдите значение выражения: а) \(12\frac{2}{5}-2\frac{2}{7}:1\frac{19}{21}\); б) \((12\frac{2}{5}-2\frac{2}{7}):1\frac{19}{21}\).

а) \(12\frac{2}{5}=\frac{62}{5}\), \(2\frac{2}{7}=\frac{16}{7}\), \(1\frac{19}{21}=\frac{40}{21}\).

\[\frac{62}{5}-\frac{16}{7}:\frac{40}{21}=\frac{62}{5}-\frac{16}{7}\cdot\frac{21}{40}=\frac{62}{5}-\frac{12}{10}=\frac{62}{5}-\frac{6}{5}=\frac{56}{5}=11\frac{1}{5}.\]

Ответ: \(11\frac{1}{5}\).

б)

\[\left(\frac{62}{5}-\frac{16}{7}\right):\frac{40}{21}=\left(\frac{434}{35}-\frac{80}{35}\right)\cdot\frac{21}{40}=\frac{354}{35}\cdot\frac{21}{40}=\frac{531}{50}=10\frac{31}{50}.\]

Ответ: \(10\frac{31}{50}\).