10 / 12 = 2 / 12 + 3 / 12 + 5 / 12
15 / 13 = 7 / 13 + 2 / 13 + 6 / 13
8 / 9 = 2 / 9 + 3 / 9 + 3 / 9
4 / 3 = 1 / 3 + 1 / 3 + 2 / 3
..................................................
6 / 3 + 4 / 3 = 10 / 3
......................................
6 / 8 = 3 / 8 + 3 / 8
.......................................
7 / 7 - 4 / 7 = 3 /7
....................................
9 / 9 - 3 / 9 - ( 3/ 9 + 2/ 9 )=9 / 9 - 3 / 9 - 5 / 9 = 1 / 9