((1 2/3) : 1 2/5 - 5/6) * 4 2/7 + (28 - 27 6/7) * 53 = 9 5/49
1) 1 2/3 : 1 2/5 = 5/3 : 7/5 = 5/3 * 5/7 = 25/21 = 1 4/21
2) 1 4/21 - 5/6 = 1 8/42 - 35/42 = 50/42 - 35/42 = 15/42 = 5/14
3) 5/14 * 4 2/7 = 5/14 * 30/7 = (5*15)/(7*7) = 75/49 = 1 26/49
4) 28 - 27 6/7 = 27 7/7 - 27 6/7 = 1/7
5) 1/7 * 53 = 53/7 = 7 4/7
6) 1 26/49 + 7 4/7 = 1 26/49 + 7 28/49 = 8 54/49 = 9 5/49