Find the expected value of the random variable with the following probability distribution... pls help no links :/

Can someone me with my hwplz(only the circled ones)

James is playing his favorite game at the arcade. after playing the game 3 times, he has 8 tokens remaining. he initially had 20 tokens, and the game costs the same number of tokens each time. the number tt of tokens james has is a function of gg, the number of games he plays

How do you use the elimination method for this question? explain, because i really want to understand!