\(PTHH:CH_4+2O_2\rightarrow\left(t^o\right)CO_2+2H_2O\\ C_2H_4+3O_2\rightarrow\left(t^o\right)2CO_2+2H_2O\\ Đặt:a=n_{CH_4}\left(mol\right);b=n_{C_2H_4}\left(mol\right)\left(a,b>0\right)\\ Có:\left\{{}\begin{matrix}22,4a+22,4b=8,96\\22,4a+44,8b=11,2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}a=0,3\\b=0,1\end{matrix}\right.\\ \%V_{CH_4}=\dfrac{a}{a+b}.100\%=\dfrac{0,3}{0,3+0,1}.100\%=75\%;\%V_{C_2H_4}=100\%-75\%=25\%\)