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? Let's be accurate as possible.
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 answer: 10.