Answer:
108
Explanation:
A number is divisible by 9 when its sum of digits is divisible by 9. Hence you're looking to add a digit to the digit 1 that makes the total be 9. That digit is 8.
When you put 8 in the units place of the number with 1 in the hundreds place, you get the smallest number greater than 100 that is divisible by 9: 108.