Вычислим:
$$1\frac{3}{7} + \frac{5}{6} = \frac{10}{7} + \frac{5}{6} = \frac{10 \cdot 6 + 5 \cdot 7}{42} = \frac{60 + 35}{42} = \frac{95}{42}$$.
$$ \frac{26}{10} \div \frac{3}{3} = \frac{26}{10} \cdot \frac{1}{3} = \frac{26}{30} = \frac{13}{15}$$.
$$1 - \frac{95}{42} - \frac{13}{15} = \frac{42 \cdot 15 - 95 \cdot 15 - 13 \cdot 42}{42 \cdot 15} = \frac{630 - 1425 - 546}{630} = \frac{-1341}{630}$$.
$$ \frac{-1341}{630} : 6 = \frac{-1341}{630} \cdot \frac{1}{6} = \frac{-1341}{3780} = \frac{-447}{1260} = -\frac{149}{420}$$.
Ответ: -149/420