Ja mialem "Ja jem z plastikowym widelcem" .
Dlaczego to nie było poprawne?
Because nobody says "z" to express using some tool. "Z" means "with" only in sense "together with" (accompanying). To express using some tool/instrument you should use Instrumental without any preposition like in the sentence above.
One Lingot for you, both for explaining and for answering in English even though the question was in Polish :)
Thanks so much!!!
Is there a distinction between sztućcem and widelcem for fork?
"sztućcem" (Instrumental of "sztuciec", usually used in plural: "sztućce") is a piece of cutlery. So it's not a synonym of a fork, as a spoon and a knife also can easily be meant by that word.
Why no z?
If you use something as an 'instrument', there is no "z", just Instrumental without any preposition.
Saying "Jem z plastikowym widelcem" would mean that the plastic fork is sitting next to you, eating as well.