Mathematics -- I don't think that word means what she think it means.
Mathematics is not same as arithmetic. Mathematics is problem solving, logic, abstract structures etc. That means, most things that are needed for programming.
Subtitles don't help just to read fast, but it also helps to learn foreign languages. In this case, mainly English. Finnish people hear English language alot and with translations subtitled. If that kind of training doesn't teach you to understand spoken English, including many common idioms, then what does?