2 1/7а+3 9/14а=11 1/7 -1 1/21-2 3/14
1) 2 1/7 = 15/7
3 9/14 =51/14
11 1/7 = 78/7
1 1/21 = 22/21
2 3/14 = 31/14
2) Приводим к общему знаменателю:
30/14 a+51/14 a = 81/14 a.
468/42 - 44/42 - 93/42 = 331/42.
3) 81/ 14 a = 331/42
a = 331*14/42*81 = 331/243.