algebra question

Question

The phone company NextFell has a monthly cellular plan where a customer pays a flat monthly fee and then a certain amount of money per minute used on the phone. If a customer uses 150 minutes, the monthly cost will be $100.5. If the customer uses 780 minutes, the monthly cost will be $384.

A) Find an equation in the form y=mx+b,y=mx+b, where xx is the number of monthly minutes used and yy is the total monthly cost of the NextFell plan.

Answer 1

Start with two-point form:

(y - 100.5) / (x - 150) = (384 - 100.5) / (780 - 150)