Step-by-step reasoning process: First first out how many euros Willie should have gotten using the official exchange rate: 70 euros / 5 euros / dollar = $14. Then multiply this quantity by 5 / 7 to find how many dollars he actually got: 14 dollars * 5 / 7 = $2 * 5 = $10.
The question and answer:
Question and answer: Willie came back from Europe with 70 euros. Normally 5 euros is worth 1 dollar, but the money exchange at the airport will only give Willie 5/7ths of the official exchange rate. How many dollars does Willie get?
The answer is 10

Step-by-step reasoning process: David's revenue for the 50 kilograms of rice is $1.20 x 50 = $60. So, his profit is $60 - $50 = $10.
The question and answer:
Question and answer: A sack of rice, which is 50 kilograms, costs $50. If David sells it for $1.20 per kilogram, how much will be his profit?
The answer is 10

Step-by-step reasoning process: The second ticket sold will cost $1 + $1 = $2. The third ticket sold will cost $2 + $1 = $3. The fourth ticket sold will cost $3 + $1 = $4. The fifth ticket sold will cost $4 + $1 = $5. The total money collected is $1 + $2 + $3 + $4 + $5 = $15. After taking profit, the total prize money will be $15 - $4 = $11.
The question and answer:
Question and answer:
Lily has 5 lottery tickets to sell. She sells the first ticket for $1. She then sells each successive ticket for a dollar more than the previous ticket. She plans to keep a $4 profit and give the remaining money as the prize. How much money will the winner of the lottery receive?
The answer is 11