The correct answer is E

Explanation

The car service uses a total of g gallons of gasoline per week, and each of the cars uses the same amount of gasoline, so each of the c cars uses g/c gallons of gasoline per week. Therefore, 5 of the cars use a total of (5g)/c gallons per week. It follows that 5 of the cars use (2)((5g)/c) equals (10g)/c gallons of gasoline in 2 weeks.