pH of Around 7.0
HBr is a strong acid so we assume it fully dissociates in water. For solutions with acids of high concentration, that means the concentration of H+ ions is equal to the concentration of the acid.
However, because your acid is of such low concentration, we must consider the self ionization of water.
The equilibrium of water is
We can get an approximate value by adding.
pH is the
by approximating we get a pH of 6.958, rounded for 2 significant figures gives you 7.0