Help Rahul, Most probably yes from the previous  year cutoff. But it's not completely sure because cutoff for jee advance vary every year on the basis of difficulty level of paper if exam will easy than cutoff will be high and if exam is tough than cutoff will be low.But if you score 80 marks in jee main than its very difficult for you to clear jee advance because jee advance is more tough than jee main . If you score only 80 marks in jee main that means your concepts are not clear so you can't do well in jee advance. work hard and achieve your goals.

Hello Rahul
Being an SC candidate, if you get 80 marks in JEE Mains 2018, considering previous year trends I would say that you most probably would be able to qualify for JEE Advanced 2018.
All the best for your results !

Hey Rahul.

Its great that you have opted for engineering and must be working hard to get through it. As far as your question is concerned, this cannot be determined before the exam. This depends upon the question paper, number of candidates and highest score. However, you can check out the cut off trends for previous years and make an idea about the scenario. The below given link will give you the cut offs

https://engineering.careers360.com/articles/jee-main-cutoff

All the best.