\[\boxed{\mathbf{878}\mathbf{\ (743)}.\ Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ \frac{11}{24} + \frac{8}{24} = \frac{11 + 8}{24} = \frac{19}{24}\]
\[2)\ \frac{23}{47} - \frac{11}{47} = \frac{23 - 14}{47} = \frac{9}{47}\]
\[3)\ \frac{3}{29} + \frac{6}{29} - \frac{8}{29} = \frac{3 + 6 - 8}{29} =\]
\[= \frac{1}{29}\]