1 7/9*3 3/8-2 5/6*10/51

Решим пример по действиям:

1) 1 7/9 = (1 * 9 + 7) / 9 = 16/9;

2) 3 3/8 = (3 * 8 + 3) / 8 = (24 + 3) / 8 = 27/8;

3) 2 5/6 = (2 * 6 + 5) / 6 = (12 + 5) / 6 = 17/6;

4) 16/9 * 27/8 = (16 * 27) / (9 * 8) = 3 * 2 = 6;

5) 17/6 * 10/51 = (17 * 10) / (6 * 51) = 10 / (6 * 3) = 10/18;

6) 6 - 10/18 = 108/18 - 10/18 = (108 - 10) / 18 = 98/18 = 49/9.

Ответ: 49/9.