What is this answer i didn’t go to school for it

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

What is the slope of the line shown below?

What ratio is proportional to 18/21