$C_\overline{n}H_{2\overline{n}}+Br_2\rightarrow C_\overline{n}H_{2\overline{n}}Br_2 $$n_X=\frac{4,48}{22,4}=0,2 mol\Rightarrow \overline{M}_X=\frac{10,5}{0,2}=52,5\Rightarrow 14\overline{n}=52,5\Rightarrow \overline{n}=3,75$
$\Rightarrow X:\begin{cases}C_3H_6:x mol \\C_4H_8:y mol \end{cases}\Rightarrow \begin{cases}x+y=0,2 \\ \frac{3x+4y}{x+y}=3,75 \end{cases}\Rightarrow \begin{cases}x=0,05 mol \\ y=0,15 mol \end{cases}$
$\Rightarrow \begin{cases}\%V_{C_3H_6}=25\% \\\%V_{C_4H_8}=75\% \end{cases}$