Phone plans A and B each have a different flat monthly rate for the first 500 text messages and a different constant rate for every additional message over 500
Plan A charges $50 monthly for 500 text messages and $66 monthly for 580 text messages.
Plan B charges $45 monthly for 500 text messages and $69 monthly for 580 text messages.
Write equations for Plan A and Plan B. Let x represent the number of messages over 500 and y represent the total monthly charges.