Questions & Answers about Штраф решили аннулировать.
Russian often uses a plural verb with no expressed subject to mean someone / people / the authorities / they in a vague, unspecified way.
So решили literally looks like they decided, but it does not mean a specific they has to be named in the sentence. In English, this is often translated more naturally as:
- They decided to cancel the fine
- It was decided to cancel the fine
This is a very common Russian pattern when the speaker does not want to name who did it, or when that is obvious from context.
It is in the accusative singular, because it is the direct object of аннулировать.
However, штраф is a masculine inanimate noun, and for nouns like that, the accusative singular looks exactly the same as the nominative singular.
So:
- nominative: штраф
- accusative: штраф
That is why the form does not change.
A useful comparison:
- Я вижу стол → стол is also masculine inanimate, so accusative = nominative
- Я вижу брата → animate masculine, so the accusative changes