866. а) 1/2-1/4; б) 5/9-1/3; в)7/10-3/5; г)16/27-1/9; д)3/5-13/45; е)1/3-8/27; ж)1/2-1/3; з)3/5-1/3; и)7/8-2/3; к)3/4-4/7; л)9/16-11/24; м)11/12-11/18.

1/2 - 1/4 = 2/4 - 1/4 = 1/4 5/9 - 1/3 = 5/9 - 3/9 = 2/9 7/10 - 3/5 = 7/10 - 6/10 = 1/10 16/27 - 1/9 = 16/27 - 3/27 = 13/27 3/5 - 13/45 = 27/45 - 13/45 = 14/45 1/3 - 8/27 = 9/27 - 8/27 - 1/27 1/2 - 1/3 = 3/6 - 2/6 = 1/6 3/5 - 1/3 = 9/15 - 5/15 = 4/15 7/8 - 2/3 = 21/24 - 16/24 = 5/24 3/4 - 4/7 = 21/28 - 16/28 = 5/28 9/16 - 11/24 = 27/48 - 22/48 = 5/48 11/12 - 11/18 = 33/36 - 22/36 = 11/36