For getting to the answer of this question, one has to know the conversion between kilometer and miles as well as the conversion between gallons and liter.
1 mile = 1.609 km
Then
16 km = 16/1.609 miles
= 9.94 miles
Again
3.785 liter = 1 gallon
then
1 liter = 1/3.784 gallons
= 0.26 liter
So
16 km/L = (9.94/0.26) miles per gallon
= 38.23 miles per gallon.
= 38 gallons
