# You just gave someone a raise. The object should be handling all the math, not you. You should be calling the giveRaise() method. That method should be able to accept a number or a percentage. That method will do all the bit-fiddling.

You forgot demotion and salary decrease, you also forgot a method to make someone's wage 20% more than someone elses and a gazillion other ways of determining someone's new salary.

So bascially I'll say to my manager I'm quitting if you don't pay me 50000 a year, he says OK and now he has to do the math so he can enter the correct increase into the system? Wy can't he just enter 50000 if that's what he wants.

If you're still not convinced, then consider the case where it's not a numeric value, it's an object value and there's no sensible way I can specify the new value as "the old value modified in this fashion". The only option is to just tell the object "here's your new value, forget about the old one". That's a mutator.