I wanna know what wil be done lastly

Can someone me with this problem i don't understand i need

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

The number if marbles of different colors stored in a hat is listed below: 4 red marbles 10 green marbles 7 blue marbles. without looking in the hat, dan takes out a marble at random. he replaces the marble and then takes out another marble from the hat. what is the probability that dan takes out a blue marble in both draws?