So, your saying that it cost $45 to rent a car AND a $12 fee.
$45+12=$57
Since your renting it for 5 days, you will have to multiply 57 and 5.
$57x5=285
$285 is your answer. (If you have daily fees)
If the fee isn't daily, then you put ($45x5)+12=n, if the fee isn't daily.....
$45x5=225
225+12=237
$237 is your answer if you don't have daily fees.
