P1\frac{7}{8}+2\frac{6}{8}

$$1\frac{7}{8}+2\frac{6}{8} = (1+2) + (\frac{7}{8} + \frac{6}{8}) = 3 + \frac{13}{8} = 3 + 1\frac{5}{8} = 4\frac{5}{8}$$

Ответ: $$4\frac{5}{8}$$