Ответ:

  1. \(1\dfrac{4}{15}-\dfrac{17}{20}=1\dfrac{16}{60}-\dfrac{51}{60}=\dfrac{5}{12}\).
  2. \(7\dfrac{4}{15}-\dfrac{7}{9}=7\dfrac{12}{45}-\dfrac{35}{45}=6\dfrac{22}{45}\).
  3. \(2\dfrac{5}{12}-\dfrac{7}{8}=2\dfrac{10}{24}-\dfrac{21}{24}=1\dfrac{13}{24}\).
  4. \(11\dfrac{1}{2}-3\dfrac{11}{18}=11\dfrac{9}{18}-3\dfrac{11}{18}=7\dfrac{8}{9}\).
  5. \(9\dfrac{2}{11}-7\dfrac{5}{9}=8\dfrac{101}{99}-7\dfrac{55}{99}=8\dfrac{46}{99}\).
  6. \(2\dfrac{6}{25}-1\dfrac{7}{10}=2\dfrac{12}{50}-1\dfrac{35}{50}=1\dfrac{27}{50}\).
  7. \(3\dfrac{1}{2}-2\dfrac{3}{4}=3\dfrac{2}{4}-2\dfrac{3}{4}=\dfrac{3}{4}\).
  8. \(12\dfrac{5}{12}-9\dfrac{13}{18}=11\dfrac{15}{36}-9\dfrac{26}{36}=2\dfrac{25}{36}\).

Ответ: а) \(\dfrac{5}{12}\); б) \(6\dfrac{22}{45}\); в) \(1\dfrac{13}{24}\); г) \(7\dfrac{8}{9}\); д) \(8\dfrac{46}{99}\); е) \(1\dfrac{27}{50}\); ж) \(\dfrac{3}{4}\); з) \(2\dfrac{25}{36}\).