Answer
(a) $y=4.35x+30.7$, slope represents the percent increase (4.35) each year.
(b) $65.5\%$
Work Step by Step
(a) Based on the given information, we have two points $(0,30.7)$ and $(12,82.9)$, assume the line equation has the form $y=mx+b$, we have $m=\frac{82.9-30.7}{12-0}=4.35$ and $b=30.7$. Thus we have $y=4.35x+30.7$. The slope the of graph represents the percent increase (4.35) each year during this period.
(b) For year 2009, we have $x=8$ and $y=4.35(8)+30.7=65.5$ per cent.
