Hello Prasenjit Das. Thanks for contacting Careers360 and we hope we will be able to answer your query. 

So, you have got 75 marks but it also depends on which category if student you are, that is, GEN or OBC-NCL or SC / ST.

The first two categories - Zero chance of getting NITs

The last category - a slim chance

I would like to direct your attention to this JEE Mains college predictor of ours that helps the students to estimate their chances of admissions in a college:

• https://engineering.careers360.com/jee-main-college-predictor?icn=jeemain-clgpd&ici=quick_links

Hope this helps you and all the best! 

Your expected Rank based on your score will be approximately between 130000 - 150000. Also, You can register for B.tech companion to know your chances in NITs/IIITs with previous year cut off by below link:
https://www.careers360.com/btech-companion

Good Luck!