1) 11 2/3 - 8 3/4 = (11-8) +(2/3-3/4) = 3+ (8-9)/12 = 3 + (-1/12) = 2 12/12 - 1/12 = 2 11/12
2) 3 1/3 + 2 5/6 = (3+2) + (1/3+5/6) =5+(2+5)/6 =5 +7/6 = 5+1 1/6 = 6 1/6
3) 2 11/12+6 1/6-4 7/12 = (2+6-4) +(11/12+1/6-7/12) = 4 +(11+2-7)/12 = 4+6/12 = 4 1/2