Answer:
OsBr2.
Explanation:
Osmium decobromide is the same as osmium bromide. This is the result of the reaction between osmium hydroxide (Os(OH)2) and hydrobromic acid (HBr) to form water and a salt (osmium bromide):
[tex]Os(OH)_2+2HBr\rightarrow OsBr_2+2H_2O.[/tex]So, osmium bromide has the formula: OsBr2.