Ответ:
а)
\[\frac{4}{9}\cdot\frac{63}{64}\cdot\frac{2}{7}=\frac{4\cdot63\cdot2}{9\cdot64\cdot7}=\frac{1}{4}.\]
б)
\[\left(\frac{1}{2}\right)^2:\frac{5}{6}:\frac{7}{15}=\frac{1}{4}\cdot\frac{6}{5}\cdot\frac{15}{7}=\frac{9}{14}.\]
в)
\[\left(1-\frac{1}{3}\right):\left(\frac{1}{3}-\frac{1}{4}\right)=\frac{2}{3}:\frac{1}{12}=\frac{2}{3}\cdot12=8.\]
Ответ: а) \(\frac{1}{4}\); б) \(\frac{9}{14}\); в) \(8\).
