a) 4/5 - 3/4 = 16/20 - 15/20 = 1/20
б) 3/10 - 2/7 = 21/70 - 20/70 = 1/70
в) 2/3 - 1/7 = 14/21 - 3/21 = 11/21
г) 5/9 - 1/3 = 5/9 - 3/9 = 2/9
д) 5/6 - 5/12 = 10/12 - 5/12 = 5/12
е) 2/13 - 0 = 2/13
Ответ: a) 1/20, б) 1/70, в) 11/21, г) 2/9, д) 5/12, е) 2/13