Answer:
about 70 years
Step-by-step explanation:
Life expectancy (e) improves by 5.7 years every 10 years, so 5.7/10 = 0.57 years per year. For t years after 2009, it can be modeled by ...
e = 0.57t +80
We want to find when that is 120:
120 = 0.57t +80
40 = 0.57t
40/0.57 = t ≈ 70.2
About 70 years from 2009, humanity may achieve a life expectancy of 120 years.
