Answer is: cobalt(II) bromide.
Bromine has oxidation number -1 (because it is nonmetal from goup XVII and gain one electron to have electron configuration as closestgas noble) , so cobalt must have oxidation number +2, because compound has neutral charge:
x + 2·(-1) = 0.
x = +2.
Cobalt(II) bromide red, solid inorganic compound, soluble in water.
