6. 45 + 6・9 – 90 20 – 2・8 + 66 51 – 8・5 – 11 81:9.7 32:4.6 49:7.8 8・9 + 8 7.3+7 6.9+6 12・0:4 5. 0.9:3 16:2:1

1. $$45 + 6 \times 9 - 90 = 45 + 54 - 90 = 99 - 90 = 9$$
2. $$20 - 2 \times 8 + 66 = 20 - 16 + 66 = 4 + 66 = 70$$
3. $$51 - 8 \times 5 - 11 = 51 - 40 - 11 = 11 - 11 = 0$$
4. $$81 : 9 \times 7 = 9 \times 7 = 63$$
5. $$32 : 4 \times 6 = 8 \times 6 = 48$$
6. $$49 : 7 \times 8 = 7 \times 8 = 56$$
7. $$8 \times 9 + 8 = 72 + 8 = 80$$
8. $$7 \times 3 + 7 = 21 + 7 = 28$$
9. $$6 \times 9 + 6 = 54 + 6 = 60$$
10. $$12 \times 0 : 4 = 0 : 4 = 0$$
11. $$0 \times 9 : 3 = 0 : 3 = 0$$
12. $$16 : 2 : 1 = 8 : 1 = 8$$

Ответ: 9; 70; 0; 63; 48; 56; 80; 28; 60; 0; 0; 8.