Introduction to Formal Logic is a textbook and a set of online practice exercises written to provide a high-quality educational resource for use in classes or for personal study, at a very reasonable cost. It covers truth-functional logic, and emphasizes important concepts so that students understand what they are doing, rather than simply manipulating symbols. It also contains two real-world applications of logic, to help students see what they are doing from a broader perspective. Currently, the book is available (as an ebook or a paperback) on Lulu.com. (Just search for it by author and title, i.e., “Dickson logic” and it should pop right up.) The online practice exercises are here.
Please bear in mind that while the book and its exercises have been in use for some time, and are mostly or entirely free of significant errors, these online practice exercises are a new addition–indeed, a work in progress–and could be less than ideal. Please feel free to share any feedback with your instructor, who will pass it along for us to consider as we continue to improve and add to these exercises.
And remember: you succeed in logic by practicing!