Anant, To qualify for JEE Mains, there is no minimum aggregate criteria. But if you want to join NITs, IIITs or CFTIs then you should score a minimum aggregate of 75% only in your 12th. 11th marks aren't considered. And then to appear for JEE Advanced which is the gateway for admission to IITs, you will need to fulfill the 75% aggregate condition. Now it is 75% for General Category and 65% for Reserved Categories. So how much you score in 12th is what matters to secure your eligibility for NITs, IIITs, CFTIs and JEE Advanced. You haven't mentioned your Categor. If you belong to General Category, then unfortunately you cannot appear for JEE Advanced or take admission to NITs, IIITs, and CFTIs. You may have to appear for Improvement exams if there is a possibility. But if you belong to Reserved Categories you are eligible.