Answer:
![P_X(1) = 9/19](https://img.qammunity.org/2020/formulas/mathematics/high-school/c49to4w9y6uocpmc8ai8q1rbcfm96rfp1b.png)
![P_X(-1) = 10/19](https://img.qammunity.org/2020/formulas/mathematics/high-school/dqjost94poy7htxolw35hjldt96m1jjcuc.png)
Explanation:
You need to take the payment and substract $1 from them, corresponding to the bet cost. With this in mind, you will win $1 with probability 18/38 = 9/19 and you will lose $1 with probability 20/38 = 10/19. With this in mind, the distribution of X is given by the following probability mass function, with range {-1,1}
![P_X(1) = 9/19](https://img.qammunity.org/2020/formulas/mathematics/high-school/c49to4w9y6uocpmc8ai8q1rbcfm96rfp1b.png)
![P_X(-1) = 10/19](https://img.qammunity.org/2020/formulas/mathematics/high-school/dqjost94poy7htxolw35hjldt96m1jjcuc.png)