Thanks for the question , i would like to inform you that NATA Merits marks are different according to reservation in diffrent university. consedering you from general category . 

 you have to secure at least 30 out of 120 or minimum 25% marks in MCQ portion and  minimum 25% marks or 20 out of 80 in drawing portion. if you are general or obc greater than or equal to 90 is required.

Candidates are expected to have 40% or more marks to qualify in the NATA exam.  They have to obtain at least 80 marks out of 200. The colleges accepting the score declares separate marks on the basis of ranks. The cutoff for NATA  2018 would be declared soon.

so 90+ is your answer

 hope i have helped you ,

Good luck for your future