\(4Na+O_2\rightarrow2Na_2O\)
x________________0,5x
\(2Ca+O_2\rightarrow2CaO\)
x____________x
\(2M+O_2\rightarrow2MO\)
2x_____________ x
\(23x40x+M_2x=11,1\)
\(31x+56x+\left(M+16\right)2x=16,7\)
\(\Leftrightarrow x\left(23+40+M_2\right)=11,1\Leftrightarrow x\left(31+M_2+32\right)=16,7\)
\(\Rightarrow\frac{63+M_2}{119+M_2}=\frac{11,1}{16,7}\)
\(\Rightarrow M=24\left(Mg\right)\)