hi 

if the math is your optional or additional subject than you can fill and get seat in the neet exam. if you will appear in the reappear examination than the result will come in the after the admission process of neet. in this way you can not take admission.

If you pass your supplementary exams, then you are eligible for NEET pertaining that you have PCB greater than 50%. 

You can get NEET 2020 if you pass supply.