Good morning can y’all help me

In the rectangle below ac=30 units what is de

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?

1) you deposit $2,500 in an account that earns 4% simple interest. how much do you earn in eight years?