Q: Studying is hard work many students find they study better when they take regular breaks.

A: Studying is hard work, many students find they study better when they take regular breaks.

Is this correct?

No. You can't join two independent clauses with a comma.

Same error as in the next one.

Sra

Studying is hard work; many students find they study better when they take regular breaks.

Is this right?

Yes, although you might want a comma between "better" and "when."

No comma between better and when.

Yes, your sentence is correct grammatically. However, it seems to be a statement rather than a question. If you intended to ask a question, you could rephrase it as "Do many students find they study better when they take regular breaks?"