Question

Solve. Assume the exercise describes a linear relationship.

When making a telephone call using a calling card, a call lasting 3 minutes costs $1.05. A call lasting 12 minutes costs $2.85. Let y be the cost of making a call lasting x minutes using a calling card. Write a linear equation that models the cost of making a call lasting x minutes.
Choose one answer.
a. y = -0.2x + 1.65
b. y = 0.2x - 9.15
c. y = 0.2x + 0.45
d. y = 5x - 279/20

Answer 1

given 2 points: (3,1.05) and (12,2.85)
the slope is:

m = (2.85-1.05)/(12-3) = 1.8/9 = .2

y-1.05 = .2(x-3)
y = .2x +.45