39. Сократите: а) (4·5)/(15·6); б) (12·14)/(49·15); в) (3·15−3·7)/27.

1. \(\dfrac{4\cdot5}{15\cdot6}=\dfrac{20}{90}=\dfrac{2}{9}\).
2. \(\dfrac{12\cdot14}{49\cdot15}=\dfrac{168}{735}=\dfrac{8}{35}\).
3. \(\dfrac{3\cdot15-3\cdot7}{27}=\dfrac{45-21}{27}=\dfrac{24}{27}=\dfrac{8}{9}\).

Ответ: а) \(\frac{2}{9}\); б) \(\frac{8}{35}\); в) \(\frac{8}{9}\).