[Sona]

₁₅P³² = ₁₆S³⁶ + β + A

I have to find out what is A.

Now β emission causes ₁₆S³². But how the mass number can be balanced? Is there any particle having negative mass number?

[mjc123]

I think your question must have a misprint; it should be ₁₆S³². See https://en.wikipedia.org/wiki/Phosphorus-32