5 / 13 = 1/13 + 4 / 13
5 / 13 = 2 /13 + 3 / 13
5 / 13 = 3 / 13 + 2 / 13
5 / 13 = 2 / 13 + 3/ 13
5 / 13 = 1 / 13 + 4 / 13
4 / 17 = 1/ 17 + 3 ? 17
4 / 17 = 2 / 17 + 2/ 17
4 / 17 = 3 / 17 + 1 / 17
1/ 17 = 1/ 17
7 / 20 = 1/20 + 6 / 20
7 / 20 = 2/ 20 = 5 / 20
7 / 20 = 3 /20 + 4 / 20
7 / 20 = 4 / 20 + 3/20
7 / 20 = 5 /20 + 2 / 20
7 /20 = 6 / 20 + 1/ 20