I'll try the 2nd eq. only. I assume you want each PSNR[i] calculated and accessible as array.
Do[PSNR[i] := 10 Log[(a[[i]]^2 P[[i]]^2/s^2), 10], {i, 100}]
Usually we do it like this (a List[]):
Table[10 Log[(a[[i]]^2 P[[i]]^2/s^2), 10], {i, 100}]
You could Enter as an input:
10 Log[(a[[i]]^2 P[[i]]^2/s^2), 10]
and Mathematic will have a button appear below it saying "Plot", if you just want to see the plot
I view .nb but i do not view .docx as i don't know what might happen if i open them and they are encrypted. Please share .nb