\(\left\{{}\begin{matrix}P+N+E=48\\P=E\\P+E=2N\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}2P+N=48\\2P-2N=0\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}P=E=Z=16\\N=16\end{matrix}\right.\)
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