Equation and slope

Question

) A long distance telephone service provider charges $30 for the first 80 minutes of international calls. For each minute over 80 minutes, the company charges $0.60 per minute. Write an equation that represents the total cost C for x minutes of long-distance calls. Calculate the cost of talking 105 minutes internationally

and

Find the slope of the line that passes through the points (2, 3) and (4, –2). Show all work.

Answer 1

C(m) = 30 + .6(m-80)= 30+.6m - 48= .6m -18

C(m) = .6m -18

C(105) = 30+.6(105-80) = 30+.6(25) = 30+15=$45

C(105) = .6(105) -18 = 63-18 = $45 for 105 minutes

(2,3), (4,-2) have a line through them with slope= -5/2