Hi everybody, can somebody tell me were I'm going wrong, this is driving me mad

Make p the subject

http://latex.codecogs.com/png.latex?...B%202%7D%20%7D =1

I get

http://latex.codecogs.com/png.latex?...B2%20%7D%7D%7D =p

Which apparently is incorrect. I'd love to show you the steps I took, but this is my first ever post and I'm really struggling with the latex workaround.(Worried)