You can make as many "manual copies" of math homework for yourself as you like.
The seemingly arbitrary number of "7" came into being because with the invention and popularity of devices for copying, private persons could make copies without considerable loss of quality.
As it was impossible to control who made a copy and whom it was given to, a compromise was found: buying a copying machine (tape recorder, cd burner, dvd burner) or empty media (empty cassette tapes, empty CDs) came with an extra fee on top to be paid by the consumer, that would go to the copyright holders in general, with the assumptions that that would cover the "normal, uncontrollable, private between friends" copying. Like if you burn your mom a CD. Or gift your girlfriend a mix tape. Or copy a page of the book and hand out the excercise to your two study buddies.
So there was a court decision that "more than seven" was more than what you would normally consider a private copy covered by this fee. If you make more than seven copies of a cassette for example, it would be okay to assume that you no longer did that "for a close friend".
Obviously, copying something from a book as you describe, by writing it down with a pencil on a notepad, is in no way "a lossless copy". Even if you type it into an app, manually copying something into another medium is not lossless. Ever. It is also for your very personal use, you don't give it to anyone, not even close friends.
So yes, you can make as many copies as you like, for yourself. If one breaks, and you make another, that is fine. If one breaks every day and you need 700 over the course of two years? Fine. But if you made 700 exact copies to give them to your "700 closest friends", that is not how the law thinks "closest friends" work. That is where the arbitrary number 7 comes from.