How Many Combinations 8 Letters How Many Combinations Are There For A ...?

How many combinations are there for a ...? - how many combinations 8 letters

Question:

certain password must be 8 characters long. (26 letters and 10 numbers are the basis of the list)

How many passwords can be enforced if they should be at least 1 digit?

The answer is 2.6123 * 10 ^ 12

an explanation?