Note
The open end of the < and > sign always opens up towards the largest amount. In this case n^2 is bigger than 18 so the expression you want is n^2>18.
This tells you that n^2 is larger than 18. Just to make it clearer suppose n = 5
Then what you get is 5^2 > 18? Is that true? 25 > 18 so yes it is true. 4^2 is not a solution because 4^2 = 16 which is smaller than 18.
One thing you should be aware of (-5)^2 > 18 is also true.
