Definition of Math isn't mathing. It is slang, and it is being used for comedy. "mathing" is not technically a word, and it is not normally a verb either. But it is playing with the words and using the repetition to reinforce what they are saying. It is saying that the math is not working properly. So the math is not doing what math should do, it is not correct, it is not behaving properly. If ... More @Wikipedia
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