1)
Cati l ulei s-au consumat in prima luna?
480:6=80 l ulei
2)
Cati l ulei s-au consumat a doua luna?
480-80=400 l ulei
400:4=100 l ulei
3)
Cati l ulei s-au consumat a treia luna?
400-100=300 l ulei
300:3=100 l ulei
4)
Cati l ulei au ramas?
480-(80+100+100)=480-280=200
R=200 l ulei