The number of people in the United states with mobile cellular phones was about 142 million in 2002 and about 255 million in 2007. if the growth in mobile cellular phones was linear, what was the approximate rate of growth per year from 2002 to 2007.
treat it as if you were given two ordered pairs
(2002, 142) and (2007, 255)
rate of growth is the same as the slope between the two points