4) \(3\frac{9}{15}+4\frac{6}{9}\)

Сократим дроби:

\(\frac{9}{15}=\frac{3}{5}=\frac{9}{15}\), \(\frac{6}{9}=\frac{2}{3}=\frac{10}{15}\).

\(3\frac{9}{15}+4\frac{6}{9}=7+\frac{9}{15}+\frac{10}{15}=7+\frac{19}{15}=8\frac{4}{15}\).

Ответ: \(8\frac{4}{15}\).