Generally, 1 US cup is taken as 236.59 ml. So 3 quarters of a cup is 177.44 ml.
(0.75 gallon) x (16 cups per gallon) = 12 cups
about 3 1/8 Cups A liter is 33.8 oz and a cup is 8oz 3/4 of a liter is 25.35 oz
12 tbsp
3 quarters of a cup of flour is 3/4 cups of flour. You answered your own question.