Пошаговое объяснение:
5/6-3/4 = 10/12 - 9/12 = 1/12;
9/14+8/21 = 27/42 + 16/42 = 43/42 = 1 1/42;
7/9+5/12-3/4 = 28/36 + 15/36 - 27/36 = 16/36 = 4/9;
2 3/4-1 5/6 = 2 9/12 - 1 10/12 = 11/12;
4 2/5+3 5/6 = 4 12/30 + 3 25/30 = 7 37/30 = 8 7/30;
7 5/12-(1 5/8+2 1/24) = 7 5/12 -(1 15/24 + 2 1/24) = 7 5/12 - 3 16/24 = 7 5/12 - 3 8/12 = 3 9/12 = 3 3/4;
