The life expectancy of an American in 2000 was 76.1 years and the life expectancy in 2007 was 78.2 years. If this trend continues find the life expectancy in teh year 2015. (Assume the trend is linear)

Do i have to find the slope first? and if so do I use (76.1, 2000) and (78.2, 2007) or do I use one of the previous and (0,2015) to find slope?

Any help would be appreciated. I'm also not sure where to go from there.

Thanks!