Answer: 4051 girls, 4862 boys and 1570 adults over 50 years of age group attended the festival.
Explanation:
Let x denotes the number of girls.
Then, the number of boys = x+811
The number of adults over 50 years of age = x-2481
Now, by considering the given scenario :-

Thus, the number of girls attended the festival = 4051,
Then number of boys = 4051+811=4862
Number of adults = 4051-2481=1570