If you are allowed to use a calculator, then use one! The square root of a number, x, is another number, y - the square root of x, which in this case is y, when multiplied by itself equals x.
For example, the following should be true if y is the square root of x:
y * y = x
substituting values for the variables:
2 * 2 = 4 (the square root of 4 is 2)
5 * 5 = 25 (the square root of 25 is 5)
etc.
Using a calculator, I get the square root of 52 as approximately 7.211 and the square root of 364 as approximately 19.08. Because these answers have decimal values, you're probably intended to use a calculator:
http://tinyurl.com/27q8kk
However, if you weren't allowed to use a calculator, then you could guess and check (assuming you can do multiplication with pen and paper - I'm using an online calculator here instead of working it out by hand for time's sake) :
http://tinyurl.com/yphuvb
Hope this helps!