Question

Which represents a side length of a square that has an area of 450 square inches?

Answer 1

Which represents a side length of a square that has an area of 450 square inches? 
I believe the answer you're looking for is 15√2 inches. 

Answer 2

we know that

the area of a square is equal to

$A=b^{2}$

where

b is the length side of the square

so

In this problem

$A=450 in^{2}$

$A=b^{2} \\ b^{2}=450\\ b=\sqrt{450} \\ b=15\sqrt{2} in$

therefore

the answer is

length of a square is equal to $15\sqrt{2} in$