Решение 2 3/4:(1 1/2-2/5)+(3/4+5/6):3 1/6

2 3/4 : (1 1/2 - 2/5) + (3/4 + 5/6) : 3 1/6 = 3.

1) 1 1/2 - 2/5 = 3/2 - 2/5 = 15/10 - 4/10 = 11/10;

2) 3/4 + 5/6 = 9/12 + 10/12 = 19/12;

3) 2 3/4 : 11/10 = 11/4 : 11/10 = 11/4 * 10/11 = 1/2 * 5/1 = 5/2;

4) 19/12 : 3 1/6 = 19/12 : 19/6 = 19/12 * 6/19 = 1/2 * 1/1 = 1/2;

5) 5/2 + 1/2 = 6/2 = 3.

Ответ: 2 3/4 : (1 1/2 - 2/5) + (3/4 + 5/6) : 3 1/6 = 3.