Question

For his long distance phone service, David pays a $7 monthly fee plus 7 cents per mintue. Last month, David's long distance bill was $13.93. For how many minutes was David billed?

Answer 1

For the long-distance service, David pays a monthly fee of $7 plus 7 cents per minute.

Let "d" represent the minutes the call lasted, and "c" the total cost of the bill, then you can express the total cost of the bill using the following expression:

`c=7+0.07d`

If the total cost of the bill was c=13.93, to determine the number of minutes David was billed for, you have to replace input this value in the equation and solve it for d

`\begin{gathered} c=7+0.07d \\ 13.93=7+0.07d \end{gathered}`

Pass 7 to the other side of the equation by applying the opposite operation

`\begin{gathered} 13.93-7=7-7+0.07d \\ 6.93=0.07d \end{gathered}`

And divide both sides by 0.07 to determine the value of d

`\begin{gathered} (6.93)/(0.07)=(0.07)/(0.07)d \\ d=99 \end{gathered}`

David was billed for 99minutes.