The cost depends upon the number of long distance minutes, m, amy uses. write the rule that describes amy's monthly cost.

Minutes(m)              Cost
0                                  20
10                                22
20                                24
50                                30

slope formula:
m = (y1 - y2) / (x1 - x2)
m = (20 - 22) / (0 - 10) = -2/-10 = 1/5 or 0.20

y = (1/5)(x) + 20

The rule that describes Amy's monthly cost is:
m = 1/5x + 20 or m = 0.20x + 20

Where x is the number of minutes spent on the call.

the distance between the school and her home is 3.6km.

explanation

12 mins = 0.2 hours = 1/5 hour

54 ÷ 3 = 18km per hour

1/5 of 18 = 3.6km per 12 mins

The answer is n divided by -5 + 1