Answer: 146,250,000
==============================================
Step-by-step explanation:
For the first and last X, there are 25 choices. This is because there are 26 letters, but we can't use the letter O. The second to last X has 26 choices.
So far we have 25*26*25 = 16250 different permutations for the letter portion of the license plate.
Now onto the number portion. The first N can't be zero, but it can be any other positive single digit number. We have 9 choices for this slot. The other N's can be zero or any other positive single digit number. We have 10 choices for each of these slots.
So we have 9*10*10*10 = 9000 different permutations for the number portion of the license plate.
Overall, there are 16250*9000 = 146,250,000 different license plates that can be formed. This is a little bit over 146 million.
--------
If you want to do the all of the multiplication as one single step, then it might look like this:
25*9*10*10*10*26*25 = 146,250,000