\(\left\{{}\begin{matrix}P+N+E=43\\P=E=Z\\Z\le N\le1,52Z\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2Z+N=43\\Z\le N\le1,52Z\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}N=43-2Z\\Z\le43-2Z\le1,52Z\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}N=43-2Z\\3Z\le43\le3,52Z\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}N=43-2Z\\12,216\le Z\le14,333\end{matrix}\right.\\ TH1:Z=P=E=13;N=17\left(lo\text{ại}\right)\\ TH2:Z=P=E=14;N=15\left(Nh\text{ận}\right)\\ A=Z+N=14+15=29\)