1) 20/51 : 15/68 + 0,6 * 1 7/18 = 1 7/9 + 5/6 = 2 11/18

2) 3 1/3 : (7 : 5 1/4) - 1 7/12 = 3 1/3 : 1 1/3 - 1 7/12 = 2 1/2 - 1 7/12 = 11/12

3) (9 5/12 - 3 3/5 - 2 1/3) : 3 1/15 = (5 49/60 - 2 1/3) : 3 1/15 = 3 29/60 : 3 1/15 =

= 1 25/184