Ответ:

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

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