Ответ:

а) \(\frac49\cdot\frac{63}{64}:\frac27=\frac49\cdot\frac{63}{64}\cdot\frac72=\frac{49}{32}\).

б) \(\left(\frac12\right)^2\cdot\frac56:\frac7{15}=\frac14\cdot\frac56\cdot\frac{15}{7}=\frac{25}{56}\).

в) \(\left(1-\frac13\right):\left(\frac13-\frac14\right)=\frac23:\frac1{12}=8\).

Ответ: а) \(\frac{49}{32}\); б) \(\frac{25}{56}\); в) 8.