Trey, Amelia, and Cho are discussing the solution set to the equation x2+9=45 .

To solve the equation \( x^2 + 9 = 45 \), we first isolate \( x^2 \):

\[
x^2 + 9 - 9 = 45 - 9
\]
\[
x^2 = 36
\]

Next, we take the square root of both sides:

\[
x = \pm 6
\]

This gives us the solutions \( x = 6 \) and \( x = -6 \). Therefore, the solution set is:

\[
\{-6, 6\}
\]

From the responses:

- Trey says the solution is \{6\} - Incorrect.
- Amelia says the solution is \{-6, 6\} - Correct.
- Cho says the solution is \{-6\} - Incorrect.

So, the correct answer is **Amelia**.