4 2/5 - 3 6/7 - 2,7 + 13 3/7 =
1. 4 2/5 - 3 6/7 = 4 14/35 - 3 30/35 = 3 49/35 - 3 30/35 = 19/35
2. 19/35 - 2,7 = 19/35 - 2 7/10 = 19/35 - 27/10 = 38/70 - 189/70=-151/70=-2 11/70
3. - 2 11/70 + 13 3/7= - 2 11/70 + 13 30/70= 13 30/70 - 2 11/70 = 11 19/70