Hey there! 
NaBr + Cl₂ → NaCl + Br₂ 
First balance Na. 
One on the left, one on the right: already balanced. 
Next balance Br. 
One on the left, two on the right. Add a coefficient of 2 in front of NaBr. 
2NaBr + Cl₂ → NaCl + Br₂ 
Lastly balance Cl. 
Two on the left, one on the right. Add a coefficient of 2 in front of NaCl. 
2NaBr + Cl₂ → 2NaCl + Br₂ 
This is our final balanced equation. 
Hope this helps!