6. \(\frac{6}{25}\cdot\frac{15}{18}\)

Сокращаем множители: \(\frac{6}{25}\cdot\frac{15}{18}=\frac{1}{25}\cdot\frac{15}{3}=\frac{15}{75}=\frac{1}{5}\).

Ответ: \(\frac{1}{5}\)