Original post was posted non-logged-in so here we go with some more details:
Sophie had 8200$ on her bankaccount.
After some time she had recived 164$ in interest rates. The rate was on 2,5%.
How many days did it take to get 164$?
8200$*0,025 = 205$
(0,025 because of 2,5% interest rate = 0,025, and 205$ = Interest rates over a year)
205$/365 = 0,5616$
(365 because of 365 days a year)
164$/0,5616$ = 292 days
(164$ because of interest rates in $ and 0,5616$ because of the reciving per day)
