а) 2/9:9/14
б) 8/11:4/33
в) 7/17:28/51
г)6/13:8/91

2/9 : 9/14 = 2/9 * 14/9 = 28/818/11 : 4/33 = 8/11 * 33/4 = 2/1 * 3/1 = 67/17 : 28/51 = 7/17 * 51/28 = 1/1 * 3/4 = 3/46/13 : 8/91 = 6/13 * 91/8 = 3/1 * 7/4 = 21/4 = 5 1/4