Записать результат действия в виде не сократимой дроби 15/12 + 1/12
13/14 + 9/14
3 5/8 - 2 7/8
2 8/15 - 1 13/15

15/12 + 1/12 = 16/12 = 8/6 = 4/3 = 1(1/3)

13/14 + 9/14 = 21/14 = 3/2 = 1(1/2) = 1,5

3(5/8) - 2(7/8) = 2(13/8) - 2(7/8) = 6/8 = 3/4 = 0,75

2(8/15) - 1(13/15) = 1(23/15) - 1(13/15)= 10/15 = 2/3