Select the letter of the correct answer.
a bus has a 180-gallon gas tank. the bus leaves gloucester county with a full tank of gas and drives 129 miles to baltimore. during the trip, the bus uses one gallon of gas every 3.3 miles.
how full is the gas tank when the bus reaches baltimore? round to the nearest percent.

a) 78% full

b)51% full

c)54% full

i'm not even sure where to start with this problem. so any is greatly appreciated. you : ).