6 3 1 - One number is correct and well placed.
7 3 0 - Nothing is correct.
1 0 2 - Two numbers are correct but wrongly placed.
6 7 8 - One number is correct but wrongly placed.
0 8 7 - One number is correct and well placed.
Can you find the 3 digit key for the number lock?
From 7 3 0 - Nothing is correct and 0 8 7 - One number is correct and well placed, it is certain that the digit 8 is one of the 3 digit key and is the second digit.
1 0 2 - Two numbers are correct but wrongly placed, we already know that zero is not one of the digits. Therefore the first digit is 2 and the last digit is 1.
The key is then 281
