This depends what you are rounding 450 to. If its to the nearest hundred it's 500. If it is to the nearest whole number or tens place then it is 450.
The answer depends on the degree of rounding.
To the nearest integer, it is 450.
To the nearest thousand, it is 0.
550
You do nothing. 450 is already rounded to the nearest ten.
450
450
450
The smallest whole number that can be rounded to 500 is 450.
450
It is already rounded to the nearest ten as 450
450
450
You do nothing. 450 is already rounded to the nearest ten.
450
450
450
450
As is. It is already rounded to the nearest tens place.
450
450