Вычислите: а) \(\frac{5}{9}a\cdot\frac{7}{10}\), если \(a=3\); б) \(\frac{1}{3}a:\frac{4}{9}\), если \(a=5\); в) \(\frac{8}{17}a\cdot\frac{51}{16}\), если \(a=2\); г) \(\frac{51}{50}a:\frac{17}{100}\), если \(a=10\); д) \(\frac{7}{11}\cdot\frac{121}{126}a\), если \(a=5\); е) \(\frac{5}{12}a\cdot\frac{3}{5}\), если \(a=4\).

1. \(\frac{5}{9}\cdot3\cdot\frac{7}{10}=\frac{7}{6}\).
2. \(\frac{1}{3}\cdot5:\frac{4}{9}=\frac{5}{3}\cdot\frac{9}{4}=\frac{15}{4}\).
3. \(\frac{8}{17}\cdot2\cdot\frac{51}{16}=3\).
4. \(\frac{51}{50}\cdot10:\frac{17}{100}=\frac{51}{5}\cdot\frac{100}{17}=60\).
5. \(\frac{7}{11}\cdot\frac{121}{126}\cdot5=\frac{35}{18}\).
6. \(\frac{5}{12}\cdot4\cdot\frac{3}{5}=1\).

Ответ: а) \(\frac{7}{6}\); б) \(\frac{15}{4}\); в) \(3\); г) \(60\); д) \(\frac{35}{18}\); е) \(1\).