In the reaction ${\mathrm{CH}}_3-\mathrm{Br}+2\mathrm{Na}+\mathrm{Br}-{\mathrm{CH}}_3\to$, the reaction is called

Wurtz reaction used for the formation of alkanes. In the given reaction, two alkyl halides (same or different) reacts with each other in the presence of Na/dry ether and form a long chain of alkanes.

${\mathrm{CH}}_3-\mathrm{Br}+2\mathrm{Na}+{\mathrm{CH}}_3-\mathrm{Br}\stackrel{\mathrm{dry} \mathrm{ether}}{\to }{\mathrm{CH}}_3-{\mathrm{CH}}_3+2\mathrm{NaBr}$