Блок №2. №5: (1/24 + 1/56) : 20/21

\(\left(\frac{1}{24}+\frac{1}{56}\right):\frac{20}{21}=\frac{1}{21}\cdot\frac{21}{20}=\frac{1}{20}\).

Ответ: \(\frac{1}{20}\)