#### Answer

The average number of digital cameras sold per year decreased (on average) by 1858.7 thousand/year from 2010 to 2013.

#### Work Step by Step

To calculate the average rate of change between two points $(x_1,y_1)$ and $(x_2,y_2)$, we use the formula:
$\displaystyle average~rate~of~change=\frac{y_2-y_1}{x_2-x_1}$
Here, we use the points $(2010,\ 7246)$ and $(2013,\ 1670)$:
$\displaystyle average~rate~of~change=\displaystyle \frac{1670-7246}{2013-2010}=\frac{-5576}{3}=-1858.7$ thousand digital cameras/year
Thus the average number of digital cameras sold per year decreased (on average) by 1858.7 thousand/year from 2010 to 2013.