Answer
a. $0.2$
b. $0.2$, $0.2\%$ per $year$.
Work Step by Step
a. To find the slope of the line segment representing liberal college freshmen, use the given coordinates of the two end points
$m=\frac{27-21}{2010-1980}=\frac{6}{30}=0.2$
b. For the period shown, the percentage of liberal college freshmen increased each year by approximately $0.2$. The rate of change was $0.2\%$ per $year$.
