Answer: 6 brands will compete in the finals.
Explanation:
Given : The flu fighters competed against 40 brands in the chicken soup country battle of the bands.
i.e. The total number of brands = 40
Also, the top 15% will complete in the all virus state finals.
[ We can write 15% as
]
It implies , the number of brands will compete in the finals is given by :-

Therefore, 6 brands will compete in the finals.