Simple, first change the 4.5% into 0.045
Thus,
900=0.045*n
900/0.045=0.045n/0.045
20,000=n
Thus, your answer is 20,000.
The answer to this is True.
This answer is correct. The absolute value of a number is its distance from 0, and we are looking for an absolute value of 1. Both -1 and 1 are 1 whole number away from 0.

is already in simplest form.
But if you meant to say

, we would combine the first two terms.
Adding/subtracting like terms is the same as adding/subtracting whole numbers.

Therefore:

Which gives us:
Did u type that by mistake