Question

The monthly cost (in dollars) of a long-distance phone plan is a linear function of the total calling time (in minutes). The monthly cost for 38 minutes of calls is $15.23 and the monthly cost for 79 minutes is $20.15 . What is the monthly cost for 59 minutes of calls?

Answer 1

Answer:

$17.75

Step-by-step explanation:

Let "m" is cost of 1 minute, and "f" is monthly fee, then

79m + f = 20.15

38m + f = 15.23

After subtracting two equations:

41m = 4.92 ==> m = $0.12 and f = $10.67

59 × 0.12 + 10.67 = 17.75