$\begin{cases}n_C=n_{CO_2}=\frac{8,96}{22,4}=0,4 mol \\n_{H}=2n_{H_2O}=\frac{2.7,2}{18}=0,8 mol\\n_{O}=2n_{CO_2}+n_{H_2O}-2n_{O_2}=2.0,4+0,8-\frac{2.11,2}{22,4}=0,6 mol \end{cases}$$\Rightarrow (X,Y):C_xH_yO_z\Rightarrow x:y:z=0,4:0,8:0,6=2:4:3$
$\Rightarrow HO-CH_2-COOH$