Let's break down and solve the problems step by step.

17. $11,000 - 3,256 + 42,680$

$11,000 - 3,256 = 7,744$ $7,744 + 42,680 = 50,424$ Answer: $50,424$

18. $129.48 + 155.67 + 0.08 + 1.24$

$129.48 + 155.67 = 285.15$ $285.15 + 0.08 = 285.23$ $285.23 + 1.24 = 286.47$ Answer: $286.47$

19. $1,386.78 - 341.23 - 156.78$

$1,386.78 - 341.23 = 1,045.55$ $1,045.55 - 156.78 = 888.77$ Answer: $888.77$

20. $400 + 32.56 + 12.468 - 301.12$

$400 + 32.56 = 432.56$ $432.56 + 12.468 = 445.028$ $445.028 - 301.12 = 143.908$ Answer: $143.908$

21. Find the missing number:

$34,783 + \text{missing number} = 68,391$ $\text{Missing number} = 68,391 - 34,783 = 33,608$ Answer: $33,608$

22. Find the missing number:

$34,567 - \text{missing number} = 2,934$ $\text{Missing number} = 34,567 - 2,934 = 31,633$ Answer: $31,633$

23. Find the missing number:

$45.167 - \text{missing number} = 12.083$ $\text{Missing number} = 45.167 - 12.083 = 33.084$ Answer: $33.084$

24. Find the missing number:

$\text{Missing number} + 122.433 = 345.824$ $\text{Missing number} = 345.824 - 122.433 = 223.391$ Answer: $223.391$

25. Immigration to Canada

In 1990, 213,334 people immigrated to Canada, and 6,057 came from the United States. To find how many came from other parts of the world: $\text{Total immigrants} - \text{U.S. immigrants} = 213,334 - 6,057 = 207,277$ Answer: $207,277$

26. Ramana's shopping

Ramana had $23.00 and spent money on:

• Shirt: $11.89
• Book: $4.99
• Candy bar: $0.85

Total spent: $11.89 + 4.99 + 0.85 = 17.73$ Money left: $23.00 - 17.73 = 5.27$ Answer: $5.27$

27. Difference in depth of caves

Depths of caves:

• Deepest cave: $1,602.03 \, \text{m}$
• Fifth deepest cave: $1,218.90 \, \text{m}$

Difference: $1,602.03 - 1,218.90 = 383.13 \, \text{m}$ Answer: $383.13 \, \text{m}$

Would you like more details on any specific problem? Here are 5 related questions you can explore:

1. How do you solve multi-step problems involving both addition and subtraction?
2. Can you explain how to verify the results of subtraction problems?
3. What is the best method to approach word problems in math?
4. How can you use estimation to check the reasonableness of a calculated answer?
5. What are the most common mistakes to avoid when solving real-world math problems?

Tip: Always write down every step in a math problem to avoid missing details or making small errors!