dmitrij330 2 3/4 : (1  1/2 - 2/5) + (3/4+5/6) : 3 1/6 = 11/4 : ( 3/2 - 2/5) + (3/4 + 5/6) : 19/6 = 
= 11/4 : ( 15/10 - 4/10) + (9/12+10/12) : 19/6 = 11/4 : 11/10 + 19/12 : 19/6 = 
= 11/4 * 10/11 + 19/12 * 6/19 = 10/4 + 6/12=10/4+2/4=12/4=3