Ответ:

-23

Пошаговое объяснение:

1) 4/5 + 19/20 = 16/20 + 19/20 = 35/20 = 7/4

2) 6 5/6 + 4 2/3 = 6 5/6 + 4 4/6 = 10 9/6 = 11 1/2

3) -1 1/7 * 7/4 = -8/7 * 7/4 = -2

4) -2 * 11 1/2 = -2 * 23/2 = -23