5) $$12 - 11\frac{6}{11}$$;

Представим 12 как $$11 + 1 = 11 + \frac{11}{11}$$. Тогда, $$12 - 11\frac{6}{11} = 11\frac{11}{11} - 11\frac{6}{11} = (11-11) + (\frac{11}{11} - \frac{6}{11}) = 0 + \frac{11-6}{11} = \frac{5}{11}$$ Ответ: $$\frac{5}{11}$$