Ответ:

9 20/23 + 3 18/23 = (9*23 + 20)/23 + (3*23 + 18)/23 = 213/23 + 87/23 = (213 + 87)/23 = 300/23

Ответ: 300/23

18 2/13 - 2 7/13 = (18*13 + 2)/13 - (2*13 + 7)/13 = 236/13 - 33/13 = (236 - 33)/13 = 203/13

Ответ: 203/13

Ответ:

1) 9 20/23 + 3 18/23 = (9*23 + 20)/23 + (3*23 + 18)/23 = 213/23 + 87/23 = (213 + 87)/23 = 300/23

2) 18 2/13 - 2 7/13 = (18*13 + 2)/13 - (2*13 + 7)/13 = 236/13 - 33/13 = (236 - 33)/13 = 203/13