Do a tree diagram.
If the first card picked is 1, then the 2nd card picked can be 2,3,4 or 5
If the first card picked is 2, then the 2nd card picked can be 1,3,4 or 5
If the first card picked is 3, then the 2nd card picked can be 1,2,4 or 5
If the first card picked is 4, then the 2nd card...