\(\left\{{}\begin{matrix}P+N+E=52\\P=E\\N=E+1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2E+N=52\\N=E+1\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}P=E=Z=17\\N=18\end{matrix}\right.\\ \Rightarrow A=Z+N=17+18=35\left(đ.v.C\right)\)
