To calculate how much money Javier has at the end of three months, we need to account for the monthly bank fee that will be applied to his account.
Javier's initial balance is $305.25, and his bank charges a fee of $7.50 each month because his balance is below $500.
We need to subtract the fee for each of the three months:
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End of Month 1: \[ 305.25 - 7.50 = 297.75 \]
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End of Month 2: \[ 297.75 - 7.50 = 290.25 \]
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End of Month 3: \[ 290.25 - 7.50 = 282.75 \]
After three months, Javier's account balance will be: \[ \boxed{282.75} \]