The answer would be 18.2 gallons because they used up 5.8 gallons, they still have 12.4 gallons that they did not use and in order to get the original amount of gas they had before the trip, you would add up 12.4 and 5.8 to get the Original amount. Hope this helps.
Well... hmmm so.. for 500 bucks you only pay a rate of say "r", and it comes down to only 28cents, or $0.28.
If 500 is say the 100%, what percentage is 0.28?

now, we're assuming the company is charging and APR, so you pay that at the end of the year. We're also assuming the year is only 360 days.
so, if you borrow 1959 on simple interest for 251 days out of 360 days, how much are you repaying?

and surely you can do that one... which is just 1959 and a few pennies.
It would be 1,2 since the left u counting by one and right is by two