Answer: Hence, Troy spend 9.09 in U.S. dollars.
Step-by-step explanation:
Since the foreign exchange rate between the U.S. dollar and the Swiss franc is 1:2.2.
It means,
1 U.S. dollar = 2.2 Swiss Franc
Now, According to question, Troy spent 20 Swiss francs to stay one night in a youth hostel.
So, 1 Swis Franc = 
20 Swiss Franc = 
Hence, Troy spend 9.09 in U.S. dollars.