What is the idiomatic way to say "doing something for somebody" when they are supposed to do it, not you ?
Say for example a school mate asks you to do the assignment she's been given.
How would you say it? "He asked me to do his assignment [don't know how to say it in place of him?]"
Following some of the comments I received, I want to clarify that the context is not necessarily academic cheating. What I'm trying to find -provided that it exists- is a translation from my language (Italian) of a subtlety in meaning when you do something for somebody who were supposed to do this thing and you decide, whatever the reason, to come forward and carry it out for her.
A couple of examples more:
- a colleague is assigned a task, but can't (because she doesn't know how) or doesn't want to do it (maybe because of laziness). Then you do the task for her (either because she asked you for help or you simply decided that somebody had to do it)
- a death sentence is handed down to someone and you step up begging to be taken instead
How would you rephrase the [for somebody] part in the two sentences above? Again, maybe I'm struggling because I can see a slight difference in meaning in Italian, when perhaps in English there is no straight translation