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 110 minutes, the monthly cost will be $73.5. If the customer uses 760 minutes, the monthly cost will be $301. 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 1

`y = 0.35x + 35`

Explanation:

Linear equation:

A linear equation has the following format:

`y = mx + b`

In which m is the slope and b is the y-intercept.

Finding the slope:

We have two points: (110, 73.5) and (760, 301).

The slope is given by the change in y divided by the change in x. So

Change in y: 301 - 73.5 = 227.5

Change in x: 760 - 110 = 650

Slope:
`m = (227.5)/(650) = 0.35`

So

`y = 0.35x + b`

Finding the y-intercept:

(760, 301) means that when
`x = 760, y = 301`. So

`301 = 0.35(760) + b`

`b = 301 - 0.35(760)`

`b = 35`

So

`y = 0.35x + 35`