Ta có: \(\left\{{}\begin{matrix}p+e+n=49\\p=e\\n=53,125\%\left(p+e\right)\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}0,53125.2p+2p=49\\p=e\\n=53,125\%.2p\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}3,0625p=49\\p=e\\n=1,0625p\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}p=e=16\\n=17\end{matrix}\right.\)
\(\Rightarrow A=p+n=16+17=33\left(u\right)\)
\(KHNT:^{33}_{16}S\)