In the two-seater category of automobiles, the Bugatti Veyron averages 10 miles per gallon, while the Smart Fortwo Electric Drive Convertible averages 107 miles per gallon. Covert these fuel efficiencies to L/100 km.

Answer 1

Are you using the US gallon or the Imperial gallon?
(one of the many problems in not using metric!)

I will assume US, so 1 US gallon = 3.97 litres
and 1 mile = 1.61 km

I will do the 2nd question, you do the first one.
1 gallons ---> 107 miles
3.97 l -----> 107 miles
1 l ----- 107/3.97 miles = 26.952..miles
1 l -----> 26.952..(1.61) km
1 l -----> 43.39 km
1(100/43.39) l ----> 43.39(100/43.39) km
2.3 l ---> 100 km

fuel efficiency = 2.3 L/100 km