Решение:
1) x - 5 - 4 = 6
x - 9 = 6
x = 6 + 9
x = 15
2) 13 - x + 9 = 16
22 - x = 16
x = 22 - 16
x = 6
3) 18 - x - 3 = 7
15 - x = 7
x = 15 - 7
x = 8
4) 11 - x + 7 = 13
18 - x = 13
x = 18 - 13
x = 5
Ответ: 15; 6; 8; 5.