I cant remember how to solve these.
A computer password consists of eight letters. How many passwords are possible? Assume there is no difference between lower-case and upper-case letters.
Recall that where .
Since the password can contain only letters, and we are to assume that there is no difference between lower and upper case we must let [if there was a difference between upper and lower case, ]. Since the password can only be 8 letters long, let .
So we see that we now have
Can you take it from here?