Question 9122
To simplify a square root, break it down into a rational part and an irrational part.

{{{5sqrt(18)}}} simplifies to {{{5*sqrt(9)*sqrt(2)}}}.  Then we simplify root 9 to 3.  When we multiply 3 and 5, we get {{{15sqrt(2)}}} (15 roots of 2).  Hope this helped.