First thing is for eligibility for giving the exam of jee mains is,

  It is mandatory for candidates to have taken 5 subjects in class XII or equivalent qualifying exam

The 5 subjects for B.Tech/ B.E. are:

1-Language, 2-Physics, 3-Mathematics, 4-Any one of (Chemistry, Biology, Biotechnology, Technical Vocational Subject), 5-Any other subjects

Second thing is you have 75 above percent and top 20percentile in your state so you are eligible for giving the jee mains