Answer
810 possible area codes
Step-by-step explanation
We have been told that there are 3 spots up for filling.
The first spot, X, can be any number from 0 through 9, that is, any of the 10 numbers.
The second spot, Y, can be any number from 0 through 9 too, but now, we can't repeat any number used for the first spot (X), so, we have 9 numbers that can fill this space.
For the third spot, Z, any digit from 1 through 9 can take this spot. That is any 9 numbers.
The number of area codes possible = 10 × 9 × 9 = 810 possible area codes
Hope this Helps!!!