Answer:
30000000
Step-by-step explanation:
there are 10 digits in the phone number
and phone numbers repeat numbers so u can have 9999999999 if that is the case
first digit must be 0 (1 pn (possible numbers)
second digit must be 2 ( 1 pn
third digit must be either 1 or 2 or 3 ( 3 pn )
Since repeated is allowed 4 to 10th digit can be any number from 0-9(10 pn)
therefore total possible numbers is
1*1*3*10*10*10*10*10*10*10 = 3*10⁷