If a customer uses 450 minutes, the monthly cost will be $211. If the customer uses 920 minutes, the monthly cost will be $399.

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 450 minutes, the monthly cost will be $211. If the customer uses 920 minutes, the monthly cost will be $399.

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

B) Use your equation to find the total monthly cost if 821 minutes are used.

Answer: If 821 minutes are used, the total cost will be ___ dollars

Answer 1

Use two-point form

(y - 211) / (x - 450) = (399 - 211) / (920 - 450)

Reduce and convert to slope-intercept form