Also try buying excel books and maybe another textbook on maths that has all the topics you are doing. I bought another year 11 general maths text book and guess what, l'm the highest in my class (in other words the entire year).
Also jess is right, don't look in the back of the textbooks!
Ask your teacher if you can spend a lunchtime or two with them so they can help you with difficult answers (sure its your lunchtime, but its also your future)
Try loooking around for a tutoring company that can tutor you once a week. You can take your work in then if you don't want to waste a lunch time.
I have tutoring once a week for maths, and its only 1 hour! Its expensive, but if u shop around l'm sure you could find a good price. I pay $35 for 1 hour. I take my work in from the week and go over with it in my tutoring class. you can get class tutoring or individual, its your choice.
Good luck with your maths and please let me know how you go!
P.S remember to practise practise practise! Although, better not buy excel until you understand the work, with excel you have to know most of the work to do the books, but try the textbooks
You can pick one up for around 20 bucks