Question 281390
This one is tricky but you want to remember one important property. 

If you have {{{sqrt(a)/sqrt(b)}}}, this is the same thing as {{{sqrt(a/b)}}}.

With that general fact in mind, we can see that
{{{sqrt(2)/sqrt(18) = sqrt(2/18)}}}

Now we want to simplify the expression inside the square root. {{{2/18 = 1/9}}}

{{{sqrt(2/18) = sqrt(1/9)}}}

Since the above fact is an equivalence relation, we see the symmetric property that
{{{sqrt(a/b) = sqrt(a)/sqrt(b)}}}

so 

{{{sqrt(1/9) = sqrt(1)/sqrt(9)}}}

The easiest way to take the square root of number is to break it up into prime factorizations and remember sqrt(1) = 1

9 is the same thing as 3 * 3

so {{{sqrt(9) = sqrt(3 * 3) = 3}}}

and {{{sqrt(1)/sqrt(9) = 1/3}}}

This was a long explanation of all the work in between, in general, when you do square roots, it's easy to go from one step to the next without showing every detail in between.

For example {{{sqrt(128)/sqrt(2) = sqrt(128/2) = sqrt(64) = 8}}}