а) 7/8 - 7/12 = (21-14)/24 = 7/24

б) 3 2/7 14 = (3 + 2/7) 14 = 314 + (214)/7 = 42 + 28/7 = 42 + 4 = 46

в) (3.7 - 1/4) : (3/7) = (37/10 - 1/4) : (3/7) = ((374 - 10)/40) : (3/7) = (148/10 - 10/10) : (3/7) = (138/10) : (3/7) = (138/10) (7/3) = 966/30 = 32/1 = 32