For this question I'm just going to use / as a square root sign because I don't know how to do it on a computer. Anyways...
So you have /45
Now you have to find a factor that is also a perfect square which is 9 (because 9x5=45)
So you now have /9x5
Since 9 is a perfect square (/9=3)
You can re write it is 3/5 which is the answer