1) 31/12
2)143/15
3) 13/3
3 - 5/12 = 2 12-5/12= 2 7/12
10 - 7/15 = 9 15-7/15= 9 8/15
7 - 8/3 = 7 - 2 2/3 = 5 - 2/3 = 4 3-2/3= 4 1/3
