1) 2/5 + 1/3 - 7/30 = 12/30 + 10/30 - 7/30 = 15/30 = 1/2
2) 3/4 - 2/9 + 5/36 = 27/36 - 8/36 + 5/36 = 24/36 = 2/3
3) 9 3/16 + 4 7/12 + 3 5/24 = 9 9/48 + 4 28/48 + 3 10/48 = 16 47/48
4) 3 17/27 - 2 13/18 = 3 34/54 - 2 39/54 = 2 88/54 - 2 39/54 = 49/54
5) 5 7/8 - 2 2/3 + 4 5/6 = 5 21/24 - 2 16/24 + 4 20/24 = 7 25/24 = 8 1/24
6) 6 8/15 + 4 5/18 - 3,6 = 6 48/90 + 4 25/90 - 3 54/90 = 7 19/90
7) ( 31 - 14 7/15) - (27 2/3 - 19 3/4) = (30 15/15 - 14 7/15) - (27 8/12 - 19 9/12) =
= 16 8/15 - (26 20/12 - 19 9/12) = 16 8/15 - 7 11/12 = 16 32/60 - 7 55/60 =
= 15 92/60 - 7 55/60 = 8 37/60