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 360 minutes, the monthly cost will be $215. If the customer uses 800 minutes, the monthly cost will be $435.

Find an equation in the form y = m x + b, where x is the number of monthly minutes used and y is the total monthly of the NextFell plan.

Answer: y = 0.5x + 35

Step-by-step explanation:

let x represent the number of minutes used by the customer in a month.

Let y represent the monthly cost for x minutes.

If we plot y on the vertical axis and x on the horizontal axis, a straight line would be formed. The slope of the straight line would be

Slope, m = (435 - 215) / (800 - 360)

m = 220/440 = 0.5

The equation of the straight line can be represented in the slope-intercept form, y = mx + c

Where

c = intercept

m = slope

To determine the intercept, we would substitute x = 360, y = 215 and m = 0.5 into y = mx + c. It becomes

215 = 0.5 * 360 + c

215 = 180 + c

c = 215 - 180

c = 35

The equation becomes

y = 0.5x + 35