"Ripened" refers to fruits, like apples. You could say "mature experience", or maybe "maturity and experience".

Personally, I would not use the word ripened to describe the word experience. As an adjective, it does not sound natural. A person with extensive ability in math might have considerable or substantial experience. I might also say, "The presence of such remarkable abilities demonstrates significant experience. They have extraordinary knowledge of math". Hope this helps

"The presence of such abilities demonstrates ripened experience and a more than ordinary knowledge of math. I have not encountered such a student in 13 years." I added an "a". You could also replace "more than" with "greater than". Otherwise I think it's OK.

Yes, thanks :)

You mean; 'Does the following sentence sound natural?'