If the 864 refers to meters, then it's already rounded to the nearest meter. If it refers to something else, you need to tell us what it is.
9 m
0.9
To round 864 to the nearest hundred, you need to look at the digit in the tens place, which is 6. Since 6 is greater than or equal to 5, you round up the hundreds digit by 1. Therefore, 864 rounded to the nearest hundred is 900.
It is: 864 divided by 2/3 = 1296
284 m