25. 5 2/3 + 3 1/4

$$5 \frac{2}{3} + 3 \frac{1}{4} = (5+3) + (\frac{2}{3} + \frac{1}{4}) = 8 + (\frac{2 \cdot 4}{3 \cdot 4} + \frac{1 \cdot 3}{4 \cdot 3}) = 8 + (\frac{8}{12} + \frac{3}{12}) = 8 + \frac{11}{12} = 8 \frac{11}{12}$$

Ответ: $$8 \frac{11}{12}$$