13. 2 +3

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: $$6 \frac{2}{5}$$