Answer:
together, they will fill 4 mugs
Explanation:
Given;
a mug holds 1/3 of a quart.
First determine how many mugs to be filled by 4/6 of a quart of fruit juice made by David;

Lastly, determine how many mugs to be filled by ⅔ of a quart of juice made by Daniel;

Therefore, together, they will fill 4 mugs