# Example 2

- Author:
- Walch Education

In 2008, about 66 million U.S. households had both landline phones and cell phones. This number decreased by an average of 5 million households per year. Use the table below to calculate the rate of change for the interval [2008, 2011].

- Determine the interval to be observed.
- Determine
. - Determine
. - Substitute
) and into the slope formula to calculate the rate of change.