a) $$4\frac{6}{17}-(\frac{11}{12}+\frac{6}{17}) = 4\frac{6}{17} - \frac{11}{12} - \frac{6}{17} = 4\frac{6}{17} - \frac{6}{17} - \frac{11}{12} = 4 - \frac{11}{12} = 3\frac{12}{12} - \frac{11}{12} = 3\frac{1}{12}$$
Ответ: $$3\frac{1}{12}$$