-7/9x+4=8/21x+6=решение

 112/- 7/9х + 4 = 8/21х + 6
- 7/9х - 8/21х = 6 - 4
- 49/63х - 24/63х = 2
- 73/63х = 2
73/63х = - 2
х = - 2 : 73/63
х = - 2 * 63/73
х = - 126/73
х = - 1 53/73

проверка:
- 7/9 * (- 126/73) + 4 = 8/21 * (- 126/73) + 6
7/9 * 126/73 + 4 = - 8/21 * 126/73 + 6
882/657 + 4 = - 1008/1533 + 6
294/219 + 4 = - 336/511 + 6
98/73 + 4 = - 48/73 + 6
4 98/73 = 5 25/73
5 25/73 = 5 25/73