The ticked answer is the answer provided by the book. Is the sum of locants rule not violated here? Please expain in detail how this compound is named.

No such rule is violated here.
See, for the main compound, we have a cyclohexane ring and all the rest groups are substituents.
For numbering, we choose the substituent having max. no of carbon atoms.
In this case, we have propyl group so 1 is alloted to it.
Next we have ethyl group and, according to the compound given, it is on 4^th carbon atom of cyclohexane.
And rest is Methyl group, which is on 3^rd carbon atom.
I guess there is no problem now, is there any? 

So we don’t even number according to alphabetical order? Is it the same with straight chain compounds?