2 1/7: 4 1/6 * 2 1/3
2 1/7 : 4 1/6 * 2 1/3 = 15/7 : 25/6 * 7/3 = 15/7 * 6/25 * 7/3 = 6/5 = 1 1/5
21/7 : 41/6 * 21/3 = 21/7 * 6/41 * 21/3 =42/41 = 1 1/41