These are not combinations!
With a password, the order of the characters is important.
Suppose that a password must satisfy the following conditions:
1) The password must be between 2 and 6 characters
2) The first character must be a letter and the last character must be a digit (0 - 9).
3) All characters except for the first or last may be either a letter or a digit.
4) Repetition is allowed.
5) They are not case sensitive.
How many passwords are possible?
The first must be a letter: 26 choices.
The last must be a digit: 10 choices.
The others must be a letter or a digit: 36 choices.