Answer:
90
Step-by-step explanation:
7 is in the unit's place. The middle digit can be any one of the 10 digits from 0 to 9. The digit in hundred's place can be any one of the 9 digits from 1 to 9. Therefore by the fundamental principle of counting there are 10 × 9 = 90 numbers between 99 and 1000 having 7 in the unit's place.
