Go through the below-provided link to check the answer key of JEE Main 2018:-

Link for all sets question paper and answer key:- https://engineering.careers360.com/articles/jee-main-answer-key

The correct responses in the answer key have to be compared to the response sheet of yours.

You must follow the official marking scheme to calculate your probable scores of JEE Main 2018.

Correct answer:- +4 marks

Wrong answer:- -1 mark

If you have calculated your JEE Main scores, go through the Carers360 rank predict to predict your ranks.

Link to the page:- https://engineering.careers360.com/-articles/jee-main-rank-predictor

( However, You have to remember that the data may not be completely correct in nature. )

All the very best and good luck.