Final answer:
The correct system of equations for the scenario where x is the number of parrotfish and y is the number of triggerfish Jenna bought is: Option 3, which includes the equations x + 4y = 280 and y = 4x.
Step-by-step explanation:
The system of equations that models the problem where x represents the number of parrotfish Jenna bought, and y represents the number of triggerfish she bought is:
- x + y = 280
- y = 4x
The correct answer to the student's question is Option 3:
\begin{cases}
x + 4y = 280 \\
y = 4x
\end{cases}
This represents a system of linear equations where the first equation sums the total number of fish bought, and the second equation gives the relation between the number of triggerfish and parrotfish.