When you're dealing with ionic compounds that are not of interest for acid - base reactions or redox reactions, you can determine their equivalent weight by looking at the charge of their constituent ions.
More specifically, if you're dealing with an ionic compound
#color(blue)("equiv. weight XY" = "molar weight X"^(+)/|"charge of X"^(+)| + ("molar weight of Y"""^(-))/|"charge of Y"""^(-)|#
You have sodium bromide,
#"equiv. weight NaBr" = "22.99 g"/|+1| + "79.9 g"/|(-1)|#
#"equiv. weight NaBr" = "102.89 g"#
As you know, equivalent weight is defined as molar weight divided by valency. What valency actually refers to depends on the reaction you're dealing with.
For an acid, its valency is the number of hydroxide ions it can react with. For a base, the valency is the number of protons (
In your case, valency simply refers to the charge (absoltue value) of the ions that make up the ionic compound.