Решить пример и объясните ( 2 - 7\10 ) : ( 5\7 + 3\14 ) = ?

(2 3/20 + 1 5/16) : (30 - 2 3/10) + 5 1/7 * 3 17/20 - 14 3/20 = 5 31/40

1) 2 3/20 + 1 5/16 = 2 12/80 + 1 25/80 = 3 37/80
2) 30 - 2 3/10 = 29 10/10 - 2 3/10 = 27 7/10
3) 3 37/80 : 27 7/10 = 277/80 : 277/10 = 277/80 * 10/277 = 1/8
4) 5 1/7 * 3 17/20 = 36/7 * 77/20 = 99/5 = 19 4/5
5) 1/8 + 19 4/5 = 5/40 + 19 32/40 = 19 37/40
6) 19 37/40 - 14 3/20 = 19 37/40 - 14 6/40 = 5 31/40