You necessarily have a #C-C# bond. How many ways can you arrange the 6 substituents, #4xxH#, and #2xxBr#, around the carbon centres.

Explanation:

You know that each #C# will have the one #C-C# bond (i.e. to each other); there are 2 ways in which the other 6 substituents can be arranged over those 2 carbon atoms. Care to hazard a guess?