923
The hundred digit is 9.
The digit to the right after 9 is 2. 2 is not up to 5. So we round down the digits after the 9 to 0s. The answer becomes 900.
If it were 5 or more than 5, we would have rounded up by adding 1 extra digit to the 9, to make the answer 1000.
So 923 to the nearest hundred is 900.
