I don't quite understand. Do you mean the third root of (8+1/3)-16? If so, then it's not a real number, because roots of negatives are weird that way.
I assume that by HCF you mean highest common factor. I also assume that "C is divisible by e" means c/e is an integer. In this case, since e is a factor of c, and the fighest factor of itself, e is the HCF.
