279. Найдите разность: a) 20 3/4 - 17; б) 13 8/11 - 5 2/11; в) 34 7/15 - 34; г) 29 19/23 - 7 2/23.

a) $$20\frac{3}{4} - 17 = (20 - 17) + \frac{3}{4} = 3 + \frac{3}{4} = 3\frac{3}{4}$$ б) $$13\frac{8}{11} - 5\frac{2}{11} = (13-5) + (\frac{8}{11} - \frac{2}{11}) = 8 + \frac{8-2}{11} = 8 + \frac{6}{11} = 8\frac{6}{11}$$ в) $$34\frac{7}{15} - 34 = (34 - 34) + \frac{7}{15} = 0 + \frac{7}{15} = \frac{7}{15}$$ г) $$29\frac{19}{23} - 7\frac{2}{23} = (29-7) + (\frac{19}{23} - \frac{2}{23}) = 22 + \frac{19-2}{23} = 22 + \frac{17}{23} = 22\frac{17}{23}$$ **Ответ:** a) $$3\frac{3}{4}$$, б) $$8\frac{6}{11}$$, в) $$\frac{7}{15}$$, г) $$22\frac{17}{23}$$