The cost of a tv dropped from $265 in 2012 to $199 in 2014. find the average rate(slope) at which the cost has been decreasing?

It has already been given in the question that the cost of tv has dropped fro $265 in 2012 to $199 in 2014. To find the average rate of decrease in the cost of tv in 2 years we have to subtract the difference in price and then divide it by 2 to get to the actual result that is needed.
Difference in price of tv = (265 - 199) dollars
                                      = 66 dollars
so the difference in price of tv in 2 years is $66
Then
The average rate of decrease in cost of tv = 66/2
                                                                    = 33
So $33 is the average rate of decrease in the price of tv between the years 2012 and 2014.