Answer: a. 126.20 gallons. 
 b. 2740 miles.
Explanation:
We will use unitary method in this question.
a) ∵ 310 miles can be covered by a car with the help of 15.5 gallons of gasoline
 ∴ 1 mile can be covered = 
 gallons
gallons 
 ∴2524 miles can be covered = 
 
 
 = 126.20 gallons
b). ∵ With 15.5 gallons of gasoline car can be driven = 310 miles
 ∴ With 1 gallon of gasoline car can go = 310/15.5 miles
 ∴ With 137 gallons can can go = (310×137)/15.5 miles
 = 2740 miles.