Let's solve these problems one by one.

1. 80 + 13 =
   $80 + 13 = 93$

2. 100 - 30 =
   $100 - 30 = 70$

3. 100 - 55 =
   $100 - 55 = 45$

4. 50 - 8 =
   $50 - 8 = 42$

5. 40 + 36 =
   $40 + 36 = 76$

6. 90 + 18 =
   $90 + 18 = 108$

7. 67 - 7 =
   $67 - 7 = 60$

8. 100 - 71 =
   $100 - 71 = 29$

9. 100 - 6 =
   $100 - 6 = 94$

Here are the answers:

• 80 + 13 = 93
• 100 - 30 = 70
• 100 - 55 = 45
• 50 - 8 = 42
• 40 + 36 = 76
• 90 + 18 = 108
• 67 - 7 = 60
• 100 - 71 = 29
• 100 - 6 = 94

Would you like further details on these calculations, or do you have any questions?

Here are some related questions for practice:

1. What is $75 + 15$?
2. How would you solve $90 - 25$ mentally?
3. What is the result of $100 - 47$?
4. Can you calculate $63 + 37$ mentally?
5. What is $100 - 19$ using subtraction?

Tip: When adding or subtracting numbers, break them into tens and units to make mental calculation easier. For example, $80 + 13$ can be split into $80 + 10 = 90$ and then add the remaining 3 to get 93.