Answer
$-78.8\ k/year$, see explanations.
Work Step by Step
Step 1. Recall the formula for the average rate of change $m=\frac{f(x_2)-f(x_1)}{x_2-x_1}$
Step 2. Based on the given conditions, we have $x_1=1980, f(x_1)=5085\ k$ and $x_2=2012, f(x_2)=2562\ k$
Step 3. Use the formula, we have $m=\frac{2562-5085}{2012-1980}\approx-78.8\ k/year$
Step 4. The above number means that the dropouts decreased at an average rate of $78.8\ k/year$ from 1980 to 2012.