A hybrid car averages 600 miles on a 12.9 gallon tank of gas. Manuel is planning a 1240-mile vacation in his hybrid car. Find how many gallons of gas he can expect to burn.

the average distance travelled by the car - 600 miles
 amount of gas used up - 12.9 gallons
therefore when he travels 600 miles he uses up 12.9 gallons
                                                                                 
for every mile the amount of gas used up - 12.9 gallons / 600 miles = 0.0215 gallons / mile 
therefore 0.0215 gallons used up per mile
                                         
so when he's going for 1240 miles - gas used up is 0.0215 gallons/ mile x 1240 miles = 26.66 gallons
                                       
amount of gas needed is 26.66 gallons