Ta có: \(p+e+n=76\)
\(\Leftrightarrow2p+n=76\) (vì \(p=e\) )
\(\Rightarrow\dfrac{n}{2p}=\dfrac{7}{12}\Rightarrow\dfrac{n}{7}=\dfrac{2p}{12}=\dfrac{n+2p}{7+12}=\dfrac{76}{19}=4\)
\(\Rightarrow n=28\)
\(\Rightarrow2p=76-28=48\) \(\Rightarrow p=24\) \(\Rightarrow e=24\)
Vậy: \(n=28\) ; \(p=e=24\)