HELP ME FIND THE VALUE OF X 20 points

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?

8.74 rounded to the nearest whole number

The lengths of the two sides of a right triangle are 5 inches and 8 inches what is the difference the possible lengths of the third side of the triangle