Answer: BLook At the pictures Please. :)
I graphed your points so you can see it visually. Look through all the pictures they show my process.
Answer
Find out the how many tiles are in each section .
To prove
Let us assume that the number of tiles are in section are be x.
As given
A mosaic at the art museum is divided into 6 sections that each contain about the same number of tiles.
There are 2,889 tiles total in the mosiac .
Than the equation becomes
6 × x = 2889

x = 481.5
Therefore the total number of tiles in each sections are 481.5 .
Percent = part/whole
It wants you to find the % of change so it's 3.25 / 3.75
And that comes out to be 0.86 (with the 6 repeating)
So you move the decimal over 2 places to find the percent.
And then it's 1 - Ans
The answer is 13.33%