3/7 x - 5/12 = -11/14 x - 3/4
6/14 x + 11/14 x = 5/12 - 9/12
17/14 x = - 1/3
x = -1/3 : 17/14
x = -1/3 * 14/17
x = -14/51
Проверим:
3/7 *(-14/51) - 5/12 = -11/14 *(-14/51) - 3/4
-2/17 - 5/12 = 11/51 - 3/4
3/4 - 5/12 = 11/51 + 6/51
9/12 - 5/12 = 17/51
4/12 = 1/3
1/3 = 1/3
Ответ: {-14/51}