I need help desperately

For f(x)=2x+3 and g(x)=x^2- 8 find (f+g) (x)

Problem 3 a bank charges a service fee of $7.50 per month for a checking account. a bank account has $85.00. if no money is deposited or withdrawn except the service charge, how many months until the account balance is negative

If there are 72 students than adults at the dance, how many adults were at the dance?