Learn Farsi: نه، من خسته نیستم.

نه (na) means "no" and is used at the beginning to answer a Yes/No question, just like in English. However, you still need to make the actual sentence negative. نیستم (nistam) is the negative verb meaning "I am not".

What is the affirmative (positive) version of نیستم?

The positive version is هستم (hastam), meaning "I am". To make the present tense "to be" verb negative, the starting هـ (h-) changes to نیـ (ni-), making it نیستم (nistam).

Could I drop the word من (I) and just say نه، خسته نیستم?

Yes, absolutely! Because the verb ending -م (-am) in نیستم already tells us "I" am the one who is not tired, the pronoun من (man) is perfectly fine to drop. Including it just adds a little emphasis.

If this is the answer, what was the Yes/No question?

The question was likely خسته هستی؟ (khaste hasti? - Are you tired?) spoken with a rising pitch at the end, or آیا خسته هستی؟ (âyâ khaste hasti?) using the question word from this lesson. To answer, you simply remove the آیا, switch the "you" verb to the "I" verb, and make it negative.