Пошаговое объяснение:

№253

а) 1/2 + 1/2 = 1

b) 4/7 + 3/7 = 1

с) 17/24 + 7/24 = 1

d) 5/18 + 11/18 + 2/18 = 1

e) 3/7 + 5/7 + 6/7 = 2

№254

a) 3/34 + 5/34 + 7/34 + 1/34 + 4/34 = 20/34 = 10/17

b) 4/29 + 3/29 + 6/29 + 7/29 + 5/29 = 25/29