Hey anonymous,
If you get the income statements of both companies you should then try to look for synergies across all the items there (both in revenue and cost). That said, it completely depends case by case, as sometimes the rationale is to boost synergies on revenues (cross sell), some other times on cutting costs (eg, duplicates HR, systems, distribution channels)
The best way to approach this cases is through a critical reasoning of the industry and companies involved so that you can get at least an hypothesis on why they are merging (this should sound natural for you after practicing some of theses cases)
best
Bruno