\(Ta.có:\\ \left\{{}\begin{matrix}P=E=Z\\P+N+E=40\\\left(P+E\right)=2N\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}2P+N=40\\2P-2N=0\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}3N=40\\2P+N=40\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}N=\dfrac{40}{3}\\P=E=\dfrac{40}{3}\end{matrix}\right.\)
Hmm em xem lại đề nha