Za+Zb+Zc=20 (1)
Za-Zb=Zc+2=> Za-Zb-Zc=2 (2)
Za+Zb-Zc=4
Din (1) si (2)=>{Za+Zb+Zc+Za -Zb-Zc=20+2=22
=> 2Za=22=>Za=22/2=>Za=11=>Za= Na(sodiu)
11-Zb=Zc+2=>11-2=Zc+Zb=> 9=Zc+Zb (3)
11+Zb+Zc=20=> Zb+Zc=20-11=9
11+Zb-Zc=4=> 7=Zb-Zc (4)
Din (3) si (4)=> {Zc+Zb+Zc-Zb=9+7
=> 2Zc=16=> Zc=8=> Zc=O(oxigen)
Za+Zb+Zc=20=>11+Zb+8=20=> Zb=20-19=> Zb=1=> Zb=H(hidrogen)
