keeping in mind that, there are 1000 milliliters in 1 Liter, and that, there are 3.79 Liters in an US gallon, assuming is an US gallon, and that there are 128 fluid ounces in 1 US gallon, then,
[tex]\bf 650~\underline{mL}\cdot \cfrac{\underline{L}}{1000~\underline{mL}}\cdot \cfrac{\stackrel{US}{\underline{gallon}}}{3.79~\underline{L}}\cdot \cfrac{128~oz}{\underline{gallon}}\implies \cfrac{650\cdot 128~oz}{1000\cdot 3.79}\\\\\\ \cfrac{83200}{3790}~oz
~~\approx~~ 21.9525065963~oz[/tex]
