Answer:
11/24
Explanation:
Devin drank 1/8 gallon of orange juice, and his brother Sam drank 1/3 of the same gallon.
So the total amount they drank is 1/8 + 1/3 = (3 + 8)/24 = 11/24 of a gallon.
Therefore, they drank 11/24 of the gallon of orange juice.