-у = -8
у = 8
................................................................
-7х = -56
х = -56 : (-7)
х= 8
проверка: -7 * 8 = -56 -56=-56
.......................................................................
11у - 9 = 8у - 30
11у - 8у = -30 + 9
3у = -21
у = -21 : 3
у = -7
проверка:
11 * (-7) - 9 = 8 * (-7) - 30
- 77 - 9 = -56 - 30
- 86 = - 86