There is a $23.78 credit on the card after 27 minutes of calls. How much credit is there after only 20 minutes in dollars.
Please see the attached file for detailed solution.
let D be the money (in dollars) remaining on the phone card. And t is the total calling time ...
The solution is comprised of step-by-step explanation of finding the linear function between the calling time and the credit remaining on a phone card. In turn, the credit remaining is calculated for a given calling time.