Respuesta :
Data:
For first 60 minutes: $19.95
plus per extra minute: $0.39
Time (in minutes): t
You have the next equation for the given situation:
C: cost
t: time
[tex]C=19.95+0.39(t-60)[/tex]a) find the cost (C) to t=155minutes
Substitute in the equation the t for 155 and calculate the C:
[tex]\begin{gathered} C=19.95+0.39(155-60) \\ C=19.95+0.39(95) \\ C=19.95+37.05 \\ C=57 \end{gathered}[/tex]For 155 minutes the cost is $57 in one month
b) find the t for C=$35
Substitute in the equation the C for 35 and solve for t:
[tex]\begin{gathered} 35=19.95+0.39(t-60) \\ 35=19.95+0.39t-23.4 \\ 35=-3.45+0.39t \\ 35+3.45=0.39t \\ 38.45=0.39t \\ \frac{38.45}{0.39}=t \\ \\ 98.58=t \end{gathered}[/tex]You can talk approximately 98.6 minutes for $35
