Answer:
1857866560
Explanation:
10 digits + 26 letters = 36 possible combination for each of the character in the password.
Since the password has a length of 6, there are
[tex]36 * 36 * 36 * 36 * 36 * 36 = 36^6 = 2176782336 [/tex] possible password combination
Since we need to make sure there's at least 1 letter and 1 number in the password, we can subtract (remove) the above result by the cases where password is made up all letters and all numbers
All numbers: [tex] 10^6 = 1000000[/tex] cases
All letters: [tex]26^6 = 308915776[/tex] cases
So the number of possible combination password where there's at least 1 letter and 1 number is:
[tex]2176782336-1000000-308915776=1857866560\approx 1.86*10^9[/tex]