а) 5/11 + 3/11 = (5+3)/11 = 8/11
б) 7/9 − 5/9 = (7-5)/9 = 2/9
в) 3 1/5 + 4 3/5 = (3+4) + (1/5 + 3/5) = 7 + 4/5 = 7 4/5
г) 7 1/7 − 2 5/7 = 6 8/7 - 2 5/7 = (6-2) + (8/7 - 5/7) = 4 + 3/7 = 4 3/7
Ответ: а) 8/11; б) 2/9; в) 7 4/5; г) 4 3/7