The task is to generate the correct answer for a given math problem.

Example Input: Problem: by selling an article for $ 195 , a person gains $ 45 . what is the gain % ?
Example Output: 30 %

Example Input: Problem: if x = 1 + √ 2 , then what is the value of x 4 - 4 x 3 + 4 x 2 + 3 ?
Example Output: 4

Example Input: Problem: 0.0008 ? = 0.02
Example Output:
0.0