An unknown ether reacts with excess of HBr to yield a single product. This implies that the ether must be either symmetrical or cyclic.
i)  $R-O-R+H-Br\to R-Br+R-OH$
     $\frac{R-O-H+H-Br\to R-Br+H_{2}O}{R-O-R+2H-Br\to 2R-Br+H_{2}O}$

ii)