so to simply a sqrt you have to break it up into factors
and you can simplify it if the factors consist of a perfect square (or a number that can be evenly square rooted, like 4 or 9)
in this case the factors of 35 are
1,5,7, and 35
none of these are perfect squares so sqrt 35 is as simplified as possible
the only thing you could do is convert it to decimal form ( which would be 5.92 rounded to the nearest hundredth) but it is not as exact as leaving it in radical form