7. Найдите значение выражения: а) \(\frac{5}{7}-0{,}7\); б) \(\frac{3}{4}+0{,}33\); в) \(\frac{1}{9}:\frac{4}{9}\); г) \(\frac{2}{7}\cdot 2\frac{4}{5}\).

1. \(\frac{5}{7}-0{,}7=\frac{5}{7}-\frac{7}{10}=\frac{50-49}{70}=\frac{1}{70}\).

2. \(\frac{3}{4}+0{,}33=0{,}75+0{,}33=1{,}08=\frac{27}{25}\).

3. \(\frac{1}{9}:\frac{4}{9}=\frac{1}{9}\cdot\frac{9}{4}=\frac{1}{4}\).

4. \(\frac{2}{7}\cdot 2\frac{4}{5}=\frac{2}{7}\cdot\frac{14}{5}=\frac{4}{5}\).

Ответ: а) \(\frac{1}{70}\); б) \(1{,}08=\frac{27}{25}\); в) \(\frac{1}{4}\); г) \(\frac{4}{5}\).