Решение выражений по порядку действий:
1. `45 + 6 * 9 - 90 = 45 + 54 - 90 = 99 - 90 = 9`
2. `20 - 2 * 8 + 66 = 20 - 16 + 66 = 4 + 66 = 70`
3. `51 - 8 * 5 - 11 = 51 - 40 - 11 = 11 - 11 = 0`
4. `81 : 9 * 7 = 9 * 7 = 63`
5. `32 : 4 * 6 = 8 * 6 = 48`
6. `49 : 7 * 8 = 7 * 8 = 56`
7. `8 * 9 + 8 = 72 + 8 = 80`
8. `7 * 3 + 7 = 21 + 7 = 28`
9. `6 * 9 + 6 = 54 + 6 = 60`
10. `12 - 0 : 4 = 12 - 0 = 12`
11. `0 - 9 : 3 = 0 - 3 = -3`
12. `16 : 2 : 1 = 8 : 1 = 8`
Ответ: 9, 70, 0, 63, 48, 56, 80, 28, 60, 12, -3, 8.