Answer:
4 gallons
Explanation:
He needs 105 over 3 to fill all the cups. 1 gallon would be 10 and 2 third cups or 32 over 3. 2 gallons would be 21 and 1 third cups or 64 over 3. 3 gallons would be 32 or 96 over 3. 4 gallons would be 42 and 2 third cups or 128 over 3. So 4 gallons would fill up all 35 of his sisters 12 ounces cups. That would leave 7 and 2 third cups that hold the same amount. His sister gets all 35 of her 12 ounces each cups filled and he gets 7 and 2 thirds of new and unused 12 ounces cups. Basically out of the 4 gallons there would be 512 ounces and his sister with all 35 cups that hold 12 ounces each she would get 420 ounces. Which would leave him with 92 ounces of juice for himself. Hope this understandable and helpful.