How many possible 3-digit area codes exist If 0 can't be the first digit, but digits can repeat?

A total of _?_ different 3-digit area codes exist.​

Step-by-step explanation:

If all numbers were used in each of the 3 places it would be 10^3= 1000.

Since 0s and 1s are not used as beginning numbers and 9 is not assigned to the middle it is as follows:

n3 - 3(n^2) = 700

I reread the question. If you mean “if" any digit could be used in any place , it would be 10^3= 1000.

step-by-step explanation:

b and c

i think the answer is d im not sure