Блок №2. №2: (1/18 − 1/21) : 5/63

\(\left(\frac{1}{18}-\frac{1}{21}\right):\frac{5}{63}=\frac{1}{126}\cdot\frac{63}{5}=\frac{1}{10}\).

Ответ: \(\frac{1}{10}\)