3/4:5/6+2 1/2*2/5-1:1 1/6

Пошаговое объяснение:

1) 3/4 : 5/6 = 3/4 * 6/5 = 18/20 = 9/10

2) 2. 1/2 * 2/5 = 5/2 * 2/5 = 10/10 = 1

3) 1 : 1. 1/6 = 1 : 7/6 = 1 * 6/7 = 6/7

4) 9/10 + 1 = 1. 9/10

5) 1. 9/10 - 6/7 = 1. 63/70 - 60/70 = 1. 3/70

ответ: 1. 3/70