Hi, I wasn't sure where to post this, figured this would do. My current textbook explains the subject well. The problems really suck however, they only cover basic calculations. Only half of the problems have answers, and a lot of the answers are wrong so it's easy for me to get stuck trying to get the answer given by the book. I have an exam very soon and would be grateful if you know some free textbook or website with problems (and answers) that I can use for practice. Thanks!