Вариант 2 1. Выполните действие: 7 16 a) 8 21 84 б)1 25 11 5 17 д)1 7 18 г) 5-315

a) $$ \frac{7}{8} - \frac{16}{21} = \frac{7 \cdot 21 - 16 \cdot 8}{8 \cdot 21} = \frac{147 - 128}{168} = \frac{19}{168} $$
б) $$1 \frac{8}{25} \cdot 1 \frac{4}{11} = \frac{33}{25} \cdot \frac{15}{11} = \frac{33 \cdot 15}{25 \cdot 11} = \frac{3 \cdot 3}{5 \cdot 1} = \frac{9}{5} = 1 \frac{4}{5}$$ в) $$1 \frac{5}{7} : 1 \frac{17}{18} = \frac{12}{7} : \frac{35}{18} = \frac{12}{7} \cdot \frac{18}{35} = \frac{12 \cdot 18}{7 \cdot 35} = \frac{216}{245}$$ г) $$5 - 3 \frac{7}{15} = 5 - \frac{52}{15} = \frac{75 - 52}{15} = \frac{23}{15} = 1 \frac{8}{15}$$ Ответ: a) $$\frac{19}{168}$$, б) $$1\frac{4}{5}$$, в) $$\frac{216}{245}$$, г) $$1\frac{8}{15}$$