I need help i never learn this

The probability that a tutor will see 0, 1, 2, 3, or 4 students is given below determine the probability distribution's missing value.

Jody bought 20 shares of amazon at the close price of $121.00. she bought 20 more shares a year later at the price of $127.00. two years later, she sold all of her shares at the price of $133.00. her broker charges $50 for each transaction. after all of these transactions, how much money did jody make?

What is the value of x in the equation 1/5x - 2/3y = 30 , when y = 15