Naima took a trip in november. she paid 2.75 a gallon for the gas she used on the trip. she filled the tank four times. the amount she bought were; 12.073gallons,12.695gallons, 11.913gallons, 12.442gallons. how much gas did she buy altogether?

It would be 17.862 gallons.  Assuming that each gas station offers the same price for gas, you can divide each total by 2.75 (the cost) giving you the gallons for each one (round to the nearest Thousandth Ex. 7.3337--->7.334), you can then add them together to get the total      
         
                                                             G=the total gallons of gas bought 
Equation:  (12.073/2.75)+(12.695/2.75)+(11.913/2.75)+(12.442/2.75)=G
                 (4.390)+(4.616)+(4.332)+(4.524)=G
                 17.862 gallons=G