Abriefcase has a three-digit lock code that does not include zero as a digit. what is the probability that the lock code consists of all even digits if the same digit is not used more than once in the lock code?

Considering that it is allowed to repeat the digits in the three-digit code, we have,
                                   10 x 10 x 10 ways 
which is equal to 1000 ways.
For the scenario that only even numbers without repetition can be included, we have,
                                     5 x 3 x 1 ways 
which is equal to 15 ways. 

The probability is therefore 15/1000 or 3/200.