Ringular has a monthly cellular plan where the customer pays a flat monthly fee and then a cost of money per minute used on the phone.

Question

If the customer uses 230 minutes, the monthly cost is $81.50. If the customer uses 950 minutes, the monthly cost is $261.50. Find a linear model of the form y=mx + b, where x is the number of monthly minutes, and y is the total monthly cost of the plan.

Answer 1

Use two-point form from Algebra 1:

(y - 81.50) / (x - 230) = (261.50 - 81.50) / (950 - 230)

Simplify and convert to slope-intercept form.