A very good textbook for discrete mathematics at an undergraduate level is the Kenneth Rosen book titled Discrete Mathematics and It'sIts Applications.
The book provides solutions to half of the problems. You can also buy the Student's Solutions Guide. I don't own it, but I would suspect that it either provides the answers to the other half of the questions or provides a step-by-step guide to solving the problems (the book only provides final answers with minimal explanations of those answers).
It's used for the two-quarter sequence in Discrete Mathematics that is taken by computer science and software engineering majors, as well as a number of mathematics programs at my university. I kept this book around even after I took the course, and I'm currently using it to brush up on my discrete math skills for my Certified Software Development Associate exam.