To solve the equation \(x^2 + 9 = 45\), we first isolate \(x^2\):
\[ x^2 = 45 - 9 \]
\[ x^2 = 36 \]
Next, we take the square root of both sides:
\[ x = \pm \sqrt{36} \]
\[ x = \pm 6 \]
This means the solution set is \({-6, 6}\).
Among the responses:
- Trey says the solution is {6} - Incorrect.
- Amelia says the solution is {-6, 6} - Correct.
- Cho says the solution is {-6} - Incorrect.
Thus, the correct answer is:
Amelia.