You are going to pay $32.50 no matter what, that is what you pay for basic cable. $4.50 is what you pay for the extras, so depending on how many premium channels you want, you will pay $4.50 for every extra channel, which is why it is 4.50x because the x is how many premium channels you purchase that month.
3 of them walk into a store, giving her a 33.333% chance of winning. By eliminating one, Tina may as well have never walked into the store, leaving Jen with a 50% chance.