Recently, I read the book What Is Mathematics? by Richard Courant. And I do the exercises in the book. When I want to check my answer, I didn't find any complete solutions through Google. (maybe I have omitted something. So if you have complete solutions by yourself or others, please tell me. Many thanks)
But by now, I have not get any complete solutions to refer, I plan to show my solutions here to provide a simple reference. My solutions may contain errors, if you find any errors, feel free to make a pull request. And if you have a different or better solution, there will be many thanks if you take your time to tell me your solution.
Maybe I will try to use programs to solve some exercises in this book. This thought is come from brendonsoto/whatIsMathematics