3-1 7/12 = 3 - 19/12 =(3 × 12 - 19 × 1)/12 = 36/12 - 19/12 = 17/12 = 1 5/12
1 5/12 + 6/2 =17/12 + 3 =(17 × 1 + 3 × 12)/12 = 17/12 + 36/12 = 53/12 = 4 5/12
ответ 4 5/12
1 2/5 + 2 3/8 =7/5 + 19/8 =(7 × 8 + 19 × 5)/40 = 56/40 + 95/40 = 151/40 = 3 31/40
3 31/40 - 0,6 = 3 31/40 - 6/10 = 151/40 - 3/5 = (151 × 1 - 3 × 8)/40 = 151/40 - 24/40 = 127/40 = 3 7/40
ответ 3 7/40