3 13.2+3 5 4 5

13. $$2\frac{3}{5}+3\frac{4}{5} = (2+3) + (\frac{3}{5} + \frac{4}{5}) = 5 + \frac{7}{5} = 5 + 1\frac{2}{5} = 6\frac{2}{5}$$.

Ответ: $$6\frac{2}{5}$$