See the percentile is a statistical interpretation of data which use to change year to year. So it isn't possible for you  or me to calculate the CET marks without the proper data.

For percentile calculation the following fomulae is used:

{(No. of students having marks less than 57) / (Total number of students that appeared in the examination)} * 100

So as you see that you have to know the data of how many students that has scored below 57 and then the total number of student that appeared for the examination. If you know this values you can calculate it.

I hope my answer helps you. All the very best for your future endeavors!