They usually release worked solutions at [
http://www.cambridge.edu.au/seniormaths ] (or you can also log in via hotmaths) when you activate your code online. They are found by clicking the resources tab or something like that (website is down atm cant remember exactly how you get them). They haven't come out yet though (like most other subjects) as they are probably still working on them??
But keep an eye out for them (when their website decides to work again) and then you should be able to download pdf's for each chapter which have in depth solutions to all questions
TIP: download all of the solutions and save them in a folder or somewhere because this year they took down the worked solutions after a little while and no one had solutions
edit: okay the website is working for me now... so on your dashboard you click on the 'more resources' icon then they will appear there soon (havent come yet)