Final answer:
To find how much tea Cassandra's brother wants, multiply the amount of tea Cassandra has (3/5 gallon) by the fraction representing her brother's request (1/4). The answer is 3/20 gallon of tea.
Step-by-step explanation:
To find how much tea Cassandra's brother wants, we need to multiply the amount of tea Cassandra has by the fraction representing her brother's request. So, \dfrac{3}{5} \times \dfrac{1}{4} = \dfrac{3}{20}
Therefore, Cassandra's brother wants \dfrac{3}{20} gallon of tea.