Thanks for the feedback. We can improve the model's focus on the task at hand and/or ask for more details if doesn't have enough context. With a bit more clarification, MathGPT outputs your answer: https://math-gpt.org/?problem_text=solve%20x%20mod%2066%20%3....
I was able to replicate your error and pushed a fix, it should be working pretty reliably now for equations that include theta. Let me know if it works for you!