Б 1) \(\frac{5}{14}=\frac{y}{42}\); 2) \(\frac{3}{25}=\frac{9}{x}\); 3) \(\frac{a}{57}=\frac{4}{19}\); 4) \(\frac{9}{c}=\frac{3}{17}\).

Решим пропорции:

1. \(\frac{5}{14}=\frac{y}{42}\)
   \(y = \frac{5 \cdot 42}{14} = 5 \cdot 3 = 15\)
   Ответ: y = 15
2. \(\frac{3}{25}=\frac{9}{x}\)
   \(x = \frac{9 \cdot 25}{3} = 3 \cdot 25 = 75\)
   Ответ: x = 75
3. \(\frac{a}{57}=\frac{4}{19}\)
   \(a = \frac{4 \cdot 57}{19} = 4 \cdot 3 = 12\)
   Ответ: a = 12
4. \(\frac{9}{c}=\frac{3}{17}\)
   \(c = \frac{9 \cdot 17}{3} = 3 \cdot 17 = 51\)
   Ответ: c = 51