P=6（y + 3q）express y in terms of p and q

Tom wants to order tickets online so that he and three of his friends can go to a water park the cost of the tickets is 16.00 per person there is also a 2.50 one-time service fee for ordering tickets online write an expression in term of n that represents the cost for n ordering tickets online

F(n + 1) = f(n) – 8. if f(1) = 100, what is f(6)?

Me. i can't figure out this question. give an explanation too. .