I ned some help!!!

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?

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).

Percent increase and decrease. original number: 45 new number: 18