3/7 = 6/6 * 3/7 = 18/42,
5/6 = 7/7 * 5/6 = 35/42,
8/21 = 2/2 * 8/21 = 16/42,
2/3 = 14/14 * 2/3 = 28/42
3/7 = 6/6 * 3/7 = 18/42,
5/6 = 7/7 * 5/6 = 35/42,
8/21 = 2/2 * 8/21 = 16/42,
2/3 = 14/14 * 2/3 = 28/42