Answer: You would have to spend 4050 yen to buy something that costs 50 dollars.
Step-by-step explanation: Since we already know the amount of yen that's equal to a dollar, all we have to do is multiply that number by the amount of dollars being spent.
This gives us: 81 * 50 = 4050. You would have to spend 4050 yen to buy something that costs 50 dollars.