Ben bir deneme üzerinde çalışmak zorunda kaldım.
- I had to work on an essay.
Onun üzerinde çalışmak zorunda kalacağız.
- We'll have to work on that.
John's in the studio working on the plans for the new house.
Leave it to me. I'll try to work on the boss to give us the day off.
... We've been working on it for a long time. ...
... We have been working on something that we believe ...