Twenty of the 50 digital video recorders (dvrs) in an inventory are known to be defective. what is the probability you randomly select an item that is not defective?

If 20 out of 50 DVRs are said to be defective, the ones that are supposedly not defective would leave a total of 30 DVRs. 
Defective - 20/50 (2/5 simplest form)
Not Defective - 30/50 (3/5 simplest form)

As shown directly above, there is a possible 30 out of 50 DVRs not defective.
Which means the probability rate is a 30/50 (3/5) chance. Percentage-wise, it'd be a 60% chance of choosing a non-defective DVR. 
You're welcome.

Depends by how many apples are in a case