$n_{O_2\text{bđ}}=\dfrac{17,28}{32}=0,54(mol)$
$\Rightarrow n_{O_2\text{pứ}}=0,54.80\%=0,432(mol)$
$2xR+yO_2\to 2R_xO_y$
$\Rightarrow n_R=\dfrac{0,432.2x}{y}=\dfrac{0,864x}{y}(mol)$
$M_R=\dfrac{16,2y}{0,864x}=\dfrac{75y}{4x}$
Thử: $(x;y)=(2;1), (1;1), (2;3), (3;4)$
(không có cặp $(x;y)$ thoả mãn)