Answer:
I know how to on a phone, it's not the same on a computer. I wish I could help, I have the same problem sometimes :(
Explanation:
The answer is most likely VoIP which means Voice over Internet Protocol. This is for example skype
D.11 If you plug in 189 for C and 15 for p. Then flip the equation to 15x+24=189, subtract 24 from both sides you get 15x=165. Finally divide both sides by 15 to get x=11. Also, when I say subtract from both sides you subtract 24 from 24 to eliminate that and 24 from 189.