hey,

i hope you are doing great ,the basic eligibility to appear for JEE mains is candidate must have passed their 10+2 from recognized board with the science subjects such as physics, chemistry and mathematics and appearing candidate are also eligible. there is no percentage required to appear for the exam ,however once cleared JEE mains and advanced , NIT and IITs do ask for 75 percentage candidate must secured in 12th standard.

for more information regarding same kindly refer to the link mentioned below

https://engineering.careers360.com/articles/jee-main-eligibility-criteria

hope this helps!