We know that Molarity , M = number of moles / volume of solution
in L
So number of moles of NaBr , n = Molarity x Volume in L
                                             Â
= 1.90 M x (55.0/1000) L
                                            Â
= 0.1045 moles
Molar mass of NaBr = At.mass of Na + At.mass of Br
                            Â
= 23+80
                            Â
= 103 g/mol
We know that number of moles = mass/molar mass
So mass of NaBr , m = number of moles x molar mass
                              Â
= 0.1045 mol x 103 (g/mol)
                              Â
= 10.8 g
Therefore the mass of sodium bromide is 10.8 g