Ответ:

  1. \(7+\frac{8}{19}=7\frac{8}{19}\);
  2. \(\frac{8}{68}+9=\frac{2}{17}+9=9\frac{2}{17}\);
  3. \(3\frac{5}{16}+4\frac{7}{16}=7\frac{12}{16}=7\frac{3}{4}\);
  4. \(12\frac{8}{13}-8\frac{4}{13}=4\frac{4}{13}\);
  5. \(5\frac{17}{21}-3\frac{8}{21}+4\frac{7}{21}=6\frac{16}{21}\);
  6. \(14\frac{8}{10}+5\frac{1}{10}-6\frac{7}{10}=13\frac{2}{10}=13\frac{1}{5}\).