"Their budget changes."
Translation:Anggaran mereka berubah.
'berubah' is an intransitive verb.
It does not have a direct object in a sentence.
'berubah' does not change someone/something else.
The subject of the sentence is undergoing the change.
'mengubah' is an active transitive verb.
It needs a direct object in a sentence.
'mengubah' is changing this object.
The subject of the sentence is doing the changing.
The object of the sentence is undergoing the change.
Anggaran mereka berubah = Their budget changed.
[Subject] = Anggaran mereka <== the subject is undergoing the change.
[Predicate] = berubah
Eva mengubah anggaran mereka = Eva changed their budget.
[Subject] = Eva
[Predicate] = mengubah
[Object] = anggaran mereka <== the object is undergoing the change.
Here is another sentence with an example: