Ответ:

  1. НОК(15, 60) = 60: 3/15 = 12/60, а 7/60 не меняется.
  2. НОК(26, 39) = 78: 5/26 = 15/78, 1/39 = 2/78.
  3. НОК(54, 45) = 270: 11/54 = 55/270, 6/45 = 36/270.
  4. НОК(42, 28, 70) = 420: 5/42 = 50/420, 7/28 = 105/420, 9/70 = 54/420.
  5. НОК(98, 112, 154) = 8624: 1/98 = 88/8624, 1/112 = 77/8624, 1/154 = 56/8624.

Ответ: 12/60 и 7/60; 15/78 и 2/78; 55/270 и 36/270; 50/420, 105/420 и 54/420; 88/8624, 77/8624 и 56/8624.