How do I match the following points that closely represents the squareroot of 27?

To determine this you have to solve the square root of 27, else you won't know what its decimal values are:
[tex]\sqrt[]{27}=3\sqrt[]{3}=5.196[/tex]Looking at the first three decimal values of the result, you can tell that is close to 5.2.
The dot that represents the square root of 27 is b.