You have 142 DVD players and sold 99 estimate how many DVD players you have left for inventory

As it's an estimation, it's better to round to the nearest ten.

142 to the nearest 10 is 140.

99 to the nearest 10 is 100.

Now you should just take away the estimate of how many you sold from the estimate of the total inventory:

140 - 100 = 40.

You have approximately 40 DVD players left.