Answer:
2 gallons
Explanation:
I'll assume the sentence should read "fill 16 one pint bottles" and not "fill a 16 one pint bottles."
1 gallon = 8 pints, by definition. We can make this a conversion factor:
(1 gallon/8 pints)
16*(1 pint) = 16 total pints soda needed to fill all the bottles
(16 pints)*(1 gallon/8 pints) = 2 gallons soda required to fill 16 one pint bottles.
Only the 2 gallon tank is needed (but either will fill the 16 one pint bottles.