Help I will give brainless !! Tell me which number is on the top and which is on the bottom

Which expression gives the area of the triangle shown 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?

Hi, can anyone show me how to do this problem? 100 points for this. in advance