Hi krishna,

Performance criteria in class 12 required is as follows:

The candidates should satisfy at least one of the following two criteria for admission to IITs:

1. Must have secured at least 75% aggregate marks in the Class XII (or equivalent) Board examination. The aggregate marks for SC, ST and PwD candidates should be at least 65%. 
2. Must be within the category-wise top 20 percentile of successful candidates in their respective Class XII (or equivalent) board examination.

So in order to give JEE ADVANCE without having 75% in 12th board,

Either you should be SC,ST Or Pwd candidate or your board's top 20 percentile is below 75%.

Good luck...