In this morning, I have a task about rewrite sentences into ones having the same meaning. There is a sentence which makes me and my classmates really confused.

This is the sentence:

• It takes my daughter two hours to study mathematics every day.

Rewrite: My daughter _________________

One of the answers we made was: -> My daughter spends two hours on studying mathematics every day.

However, my teacher told us that it might be incorrect to use "spend sth on" in this case ("spend sth doing sth" was correct) and sth in "spend sth on" did not refer time.

It was just "maybe" because she was not sure and she expected that anyone could give her proof and reasonable explanations. Does my teacher right? How to use spend correctly? Please give your opinions and comments.