A function f is even if f(-x) = f(x) and odd if f(-x) = -f(x).
In this case, though, for any x in RR where x!=0, we have that one of sqrt(x) and sqrt(-x) is real, and the other is imaginary. Thus, in all such cases, 3sqrt(-x)!=3sqrt(x) and 3sqrt(-x)!=-3sqrt(x), meaning 3sqrt(x) is neither even nor odd.