First take $92.50 and multiply by 10 for each month it was spent. That equals $925.
Then take $36.50 and multiply that by 10 as well because he used it for 10 months. You get $365. But remember, the $365 is what was taken OUT of his bank account. So, subtract 925 - 365 and get 560. 1/2 means one half. That means take half of our answer, 560. 560 divided by 2 is 280.
So, your answer is $280.00