Maths.com/,/,/,that's has everything I can find, but I suggest that moderators don't expect from these websites. There is only one way in mathematics, do more problems and sum up those important concepts. It's best to make a picture and do the questions in a targeted way. Can you ask the teacher if you don't understand? If the moderator has the conditions, you'd better find a teacher to tutor you, like some personalized educational institutions, such as "Xueda Education".