I'll go through each problem step-by-step for clarity:

1. (25 + 30) × 10 $25 + 30 = 55$ $55 \times 10 = 550$ The correct answer is 550.

2. 80 + (4 + 4) - 7 $4 + 4 = 8$ $80 + 8 - 7 = 81$ The correct answer is 81.

3. 266 - 6 × 3 + 3

   • Follow the order of operations (PEMDAS/BODMAS). $6 \times 3 = 18$ $266 - 18 + 3 = 251$ The correct answer is 251.

4. 9 × (47 - 22) ÷ 25 $47 - 22 = 25$ $9 \times 25 = 225$ $225 \div 25 = 9$ The correct answer is 9.

5. 10 × 66 + 66 $10 \times 66 = 660$ $660 + 66 = 726$ The correct answer is 726.

6. 5 - 3 + 10 - 5

   • Solve from left to right. $5 - 3 = 2$ $2 + 10 = 12$ $12 - 5 = 7$ The correct answer is 7.

7. 18 + (8 - 5) + 7 × 2 + 6 × (4 + 2) $8 - 5 = 3$ $4 + 2 = 6$ $7 \times 2 = 14$ $6 \times 6 = 36$ $18 + 3 + 14 + 36 = 71$ The correct answer is 71.

8. 3 + 12 ÷ 4 + 3 × 5

   • Follow the order of operations. $12 \div 4 = 3$ [ 3 \times 5 =