Let x be the number of texts (amount of texts) Carly does in a month.
Let y be the "total" amount Carly will have to pay in a month.
Then, as per the TURKEY plan, Carly's monthly total cost will be represented by the equation as shown:
As we can clearly see in the above equation even if Carly does not text a single message (when x=0), even then they will have to pay $20 for that month.
For the GOBBLE plan, the equation will be: .
In this plan as there is no fixed charge, Carly wont have to pay anything extra if they dont make a call.