в) 12:25 = \(\frac{7}{15}\): x;
Преобразуем пропорцию:
\(\frac{12}{25} = \frac{\frac{7}{15}}{x}\)
\(12 \cdot x = \frac{7}{15} \cdot 25\)
\(12x = \frac{175}{15} = \frac{35}{3}\)
\(x = \frac{35}{3} : 12 = \frac{35}{3} \cdot \frac{1}{12} = \frac{35}{36}\)
Ответ: \(x = \frac{35}{36}\)