Hello.
It is not possible to calculate the marks for individual subjects through a given percentile. But, you can calculate your marks for each subject by checking your answers with the Answer Key provided by The National Testing Agency (NTA). You can find the Answer Key on the official website.
You can go to this link to download the Answer key: https://engineering.careers360.com/articles/jee-main-answer-key
I hope this helps.
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