Х:2,5 = 8 4/7 : 2 1/7
х : 2 5/10 = 60/7 : 15/7
х : 2 1/2 = 60/7 * 7/15
х : 5/2 = 60/15
х : 5/2 = 4
х = 4 * 5/2
х = 20/2
х = 10
2 1/7 : 3/28 = 3 1/3х : 1,5
15/7 * 28/3 = 10/3 х : 1 5/10
20/1 = 10/3х : 1 1/2
20 = 10/3х : 3/2
20 = 10/3х * 2/3
20 = 20/9х
х = 9