I have difficulties with understanding what preposition should I use after a verb "to work" when I'm talking about spending time on development/resolvment of a specific task. Should I say "to work on a task" or "to work at a task" And is there any difference at all?
For instance, Oxfords Learner's Dictionaries says that both are fine if we are implying doing something that involves physical or mental effort, especially as part of a job (which is basically the meaning I want to use). Yet, I'm still not quite sure because if we take into consideration meanings of such phrasal verbs as "to work on sth." and "to work at sth.", we can see the difference. Does the difference in meanings of these phrasal verbs transfer to a regular verb "to work"?