b) 5 i 14/24- 3 i 9/24 = 2 i 5/24
c) 2 i 8/20 - 15/20 = 1 i 28/20 - 15/20 = 1 i 13/20
d) 1 i 4/18 - 15/18 = 22/18 - 15/18 = 7/18
