Final answer:
Dennis used a total volume of 5/6 glass for the calamansi juice mixture.
Step-by-step explanation:
To determine the volume of the mixture, we need to add the individual volumes of each component. Given that Dennis mixed 2/3 glass of water, 1/4 glass of pure calamansi juice, and 1/12 glass of sugar, we can add these fractions together to find the total volume of the mixture. The common denominator for these fractions is 12. So, when we add 2/3, 1/4, and 1/12, we get a total volume of 5/6 glass.