a) \frac{5}{95} = \frac{5}{5 \cdot 19} = \frac{1}{19}
б) \frac{60}{90} = \frac{2 \cdot 30}{3 \cdot 30} = \frac{2}{3}
в) \frac{4}{21} = \frac{4}{3 \cdot 7} = \frac{\frac{4}{3}}{7}
г) \frac{36}{42}= \frac{6 \cdot 6}{6 \cdot 7} = \frac{6}{7}
д) \frac{100}{200} = \frac{1 \cdot 100}{2 \cdot 100} = \frac{1}{2}
e) \frac{16}{40} = \frac{2 \cdot 8}{5 \cdot 8} = \frac{2}{5}
Ответ: a) 1; б) 3; в) \frac{4}{3}; г) 42; д) 1; e) 5