a) 3/10 + 8/15 = 9/30 + 16/30 = 25/30 = 5/6
b) 5/6 - 4/9 = 15/18 - 8/18 = 7/18
c) 3/8 + 5/12 = 9/24 + 10/24 = 19/24
d) 7/12 - 4/15 = 35/60 - 16/60 = 19/60
e) 5/9 + 7/12 = 20/36 + 21/36 = 41/36 = 1 i 5/36
f) 8/9 - 7/15 = 40/45 - 21/45 = 19/45
g) 1/6 + 5/8 = 4/24 + 15/24 = 19/24
h) 17/20 - 8/15 = 51/60 - 32/60 = 19/60
i) 11/18 - 5/12 = 22/36 - 15/36 = 7/36