1) 2 3/4 : (5 1/2 - 4 2/5) = 11/4 : (11/2 - 22/5) = 11/4 : 11/10 = 11/4 * 10/11 = 1/2 * 5 = 5/2 = 2 1/2

2) (4 3/8 + 12 7/24) : 16 2/3 = ((4+12) + (3/8+7/24)) : 16 2/3 = (16 + 2/3) : 16 2/3 = 16 2/3 : 16 2/3 = 1

3) (5 1/6 + 7 5/6) : (9 2/3 - 2 11/22) = ((5+7) + (1/6+5/6)) + (29/3-55/22) = (12+1) : 43/6 = 13 * 6/43 = 78/43 = 1 35/43

4) (6 2/3 - 5 1/4) : ( 2 3/4 + 4 1/6) = (20/3-21/4) : ((2+4)+(3/4+1/6)) = 17/12 : (6+11/12) = 17/12 : 6 11/12 = 17/12 : 83/12 = 17/12 * 12/83 = 17 * 1/83 = 17/83