Please solve the programming task below using a self-contained code snippet in a markdown code block.

Given two integers, num and t. A number is achievable if it can become equal to num after applying the following operation:

Increase or decrease the number by 1, and simultaneously increase or decrease num by 1.

Return the maximum achievable number after applying the operation at most t times.
 
Please complete the following python code precisely:
```python
class Solution:
    def theMaximumAchievableX(self, num: int, t: int) -> int:
```