Someone i don't know how i got #7 or how to solve it.

What is the value of x in the diagram below?

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?

Graph the equationy=x^2 -[tex]y = x^{2} - 2[/tex]