When I went through selection just over 2 years ago I failed the maths test first time, went away did lots of practise on the stuff I couldn't do and fluked 15 out of 15. It's not that difficult so don't stress about it to much.
As much as I dislike reading TheBeak's comments, a fair amount of it is true, the reality is harsh at the moment. No movement in the hold pool expected until possibly the end of the year. Even then nothing has been announced, at the moment I am counting my lucky stars that my loan is unsecured and that the interest rate has dropped from 8.8% to around 3%. The recession isn't all bad then!