Answer:
[tex]R(t) = 200 - *t[/tex]
Step-by-step explanation:
This problem can be modeled by simple decreasing first order function.
This function has the following format
[tex]R(t) = R_{0} - a*t[/tex]
In which R(t) is the remaining time, in minutes, [tex]R_{0}[/tex] is the initial remaining time, and a is the angular coefficient of the function.
In your problem, the prepaid phone card has a credit of 200 minutes, so [tex]R_{0} = 200[/tex]. At each minute, the amount of time remaining will decrease by 1, so the angular coefficient is 1, a = 1.
We are left with:
[tex]R(t) = 200 - *t[/tex]
