Answer:
the number of adult ticket sold is 570

Step-by-step explanation:
Let x represent the number of adult ticket and y represent the number of child's ticket.
Given that he charges $5 for an adult's ticket and $2 for a child's ticket.
For one event, he sold 785 tickets.
So, we have;

he sold 785 tickets for $3280.
Then;

let us solve by substitution.
make y the subject of formula in equation 1 and substitute to equation 2;

substituting to equation 2;

Therefore, since x represent the number of adult tickets sold, then the number of adult ticket sold is 570
