+ / - / ?
was / were + Ving
Affirmative sentences (+): was/were + Ving 
Subject was / were Ving
I was working
We were working
You were working
They were working
He was working
She was working
It was working
Negative sentences (-): was / were + not + Ving 
Subject was / were not Ving
I was not working
We were not working
You were not working
They were not working
He was not working
She was not working
It was not working
was not = wasn't
were not = weren't
Interrogative sentences (?): ... was / were + S + Ving … ?
(QW) was / were Subject Ving "what / where / when" ?
  Was I working   ?
  Were we working   ?
Where were you working yesterday at 8 o'clock ?
  Were they working   ?
  Was he working when the children came ?
  Was she working   ?
  Was it working   ?
Short answers:
Yes, S + was / were. 
No, S + wasn't / weren't. 
Yes, Subject was. / were.    No, Subject wasn't. / weren't.
Yes, I was.   No, I wasn't.
Yes, we were.   No, we weren't.
Yes, you were.   No, you weren't.
Yes, they were.   No, they weren't.
Yes, he was.   No, he wasn't.
Yes, she was.   No, she wasn't.
Yes, it was.   No, it wasn't.
In short answers we use pronouns (I, we, you, they, he, she, it)
— Was Adam working yesterday at 9 o'clock?
— No, he wasn't.
(Not: No, Adam wasn't.) 
Ving — Verb ending in "-ing" (Present Participle). E.g. writing, going, listening, etc.
Revise how to add "ing" to a verb here.
S — Subject of the sentence
QW — Question word