Pllzzz help me w this!!

Galen sold tickets of his church’s carnival for a total of $2,820. children’s tickets cost $3 each and adult tickets cost $5 each. the number of children’s tickets sold was 30 more than 3 times the number of adult tickets slod. how many children’s ticket and how many adult tickets did he sell?

Explain how you can find the missing fraction in 3 4/5 / (blank) 2 5/7. then find the missing fraction.

Answer! if you don’t mind, can you explain