Ta có: \(\left\{{}\begin{matrix}p+e+n=34\\p=e\\p+e=1,8333n\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2p+n=34\\p=e\\2,8333n=34\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}p=e=11\\n=12\end{matrix}\right.\)
\(\Rightarrow A=p+n=11+12=23\left(u\right)\)