Ответ:

  1. 11/18 − 2/9 = 11/18 − 4/18 = 7/18.
  2. 7 − 6 1/2 = 7 − 6.5 = 1/2.
  3. 2 5/9 + 5 7/15 = 7 + 25/45 + 21/45 = 8 1/45.
  4. 8 9/20 − 4 8/15 = 169/20 − 68/15 = 507/60 − 272/60 = 3 11/12.
  5. 4 · 1/4 = 1.
  6. 18/39 · 3 1/4 = 6/13 · 13/4 = 1 1/2.
  7. 15/16 : 5/8 = 15/16 · 8/5 = 3/2.
  8. 4 1/5 : 1 1/4 = 21/5 · 4/5 = 4 9/25.