2) 8-(5+1)==

a) $$8\frac{5}{6} - (5\frac{1}{2} + 1\frac{7}{8})$$

$$5\frac{1}{2} + 1\frac{7}{8} = 5\frac{4}{8} + 1\frac{7}{8} = 6\frac{11}{8} = 7\frac{3}{8}$$

$$8\frac{5}{6} - 7\frac{3}{8} = 8\frac{20}{24} - 7\frac{9}{24} = 1\frac{11}{24}$$

Ответ: $$1\frac{11}{24}$$