2/5 : 5/7 = 2/5 * 7/5 = 14/25
1/4 : 1/2 = 1/4 * 2/1 = 2/4 = 1/2
2 : 1/7 = 2 * 7/1 = 14
4 : 2/3 = 4 * 3/2 = 12/2 = 6
4/9 : 2 = 4/9 * 1/2 = 4/18 = 2/9
5/7 : 3 = 5/7 * 1/3 = 5/21
1/4 : 3 1/2 = 1/4 : 7/2 = 1/4 * 2/7 = 2/28 = 1/14
3 1/2 : 2 1/3 = 7/2 : 7/3 = 7/2 * 3/7 = 3/2 = 1 1/2