Help me plz I suck at math

Option 1: $30 an hour plus a nonrefundable deposit of $50 option 2: $20 an hour plus a nonrefundable deposit of $75 kyle is renting a jetski for the day. if he can rent the jetski in one hour increments, what is the minimum number of hours must he rent the jetski for option 2 to be a better deal then option 1?

In the polynomial below, what number should replace the question mark to produce a difference of squares? x2 + ? x - 36

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