Password must have length between 6 and 8.
Each password contains at least 1 digit [0-9].
Other characters either upper case or lower case.
So we have 62 different possiblities in each position, am i correct? . Yes!
Consider the 6-character passwords.
With no restrictions, there are: . possible passwords.
But the password must contain at least one digit.
We must eliminate the passwords with no digits (all letters).
. . There are: . passwords which have no digits.
Hence, there are: . six-character passwords
. . which contain at least one digit.
Similarly, there are:
. . seven-character passwords with at least one digit
. . eight-character passwords with at least one digit.