Hy Swathi !! 

Yes of course you can give your 12th exams again for better results. I had a student with similar issue. He gave 12th exams this year for better result.

What you have to do is to select 3 subjects in which you are sure that you can improve and get good marks ( more than earlier) and give the exams again . this can increase your overall percentage.

All the best !! 

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