(15 1/3 - 8 5/18 ) * 2 4/7 : 6 1/21 - 2 5/8 = 3/8,
1) 15 1/3 - 8 5/18 = 46/3 - 149/18 = 276/18 - 149/18 = 127/18 = 7 1/18,
2) 7 1/18 * 2 4/7 = 127/18 * 18/7 = 127/7 = 18 1/7,
3) 18 1/7 : 6 1/21 = 127/7 : 1221/7 = 7/21 = 127/7 * 21/127 = 3,
4) 3 - 2 5/8 = 2 8/8 - 2 5/8 = 3/8,
8,25 : 1,1 - (3 - 2,8 * 3/7) : 0,6 = 4,5,
1) 8,25 : 1,1 = 7,5,
2) 2,8 * 3/7 = 28/10 * 3/7 = 6/5 = 1 1/5 (или 1,2),
3) 3 - 1,2 = 1,8,
4) 1,8 : 0,6 = 3,
5) 7,5 - 3 = 4,5