You need to score 75% in your 12th for gaining eligibility for admission in IITs. With 75.6%, you are safe. However, this is just one of the elligibility criteria. You need to fulfil 5 criteria to be eligible for being considered for JEE Advanced. They are as follows:

1. You need to be among top 250,000 Candidates of JE Mains score across all Categories
2. No upper age limit as for now
3. You can attempt JEE Advance not more than twice in 2 consecutive years
4. Your 12th performance
5. If you have been admitted earlier in an IIT, you are not eligible.

Please visit our page for complete information for eligibility criteria at: https://engineering.careers360.com/articles/jee-advanced-eligibility-criteria