i realise the exam was a while ago but i spoke to my accounting teacher about this question. he went and asked an economics teacher at my school who is on the VCAA Accounting exam board. This teacher said there had been much discussion about the question already and that the VCAA will accept a number of answers. The starting balance either way is $20,000 and both $10,000 capital contributed and $30,000 capital injected in the Financial Activites section will most likely be accepted. This is because it was unclear whether the 30,000 in the cash reciepts journal included the starting capital.
The starting balance couldn't technically be 0, as this would breach the entity principle, as registration fees (and other business commencing fees) are business expenses. I gather that the injection of capital essentially commences the business and thus is the opening balance.
This is what i was told from my accounting teacher after he spoke to a VCAA Accounting exam board member.
I hope this clears up any questions, however i wouldn't treat this information as gospel
-S