Please check the sentence for grammar.
Son opération préférées dans les mathématiques est la multiplication.
I'm not sure about son or sa.
Everything is correct!
(Tout est correct)
To determine if you should use "son" or "sa" in the sentence, you need to know the gender of the noun it is referring to.
In this case, the noun "opération" is feminine, so you should use "sa" instead of "son." Therefore, the correct sentence is:
"Sa opération préférée dans les mathématiques est la multiplication."
Additionally, there is a spelling mistake in the sentence. The correct form of the word "préférées" should be "préférée" since the noun "opération" is singular.