The file you've uploaded appears to contain mathematical content. Let me extract and analyze it to provide the solutions to the problems.

I'll begin by reviewing the first 20 questions and providing their solutions. If there are specific problems you'd like to focus on, please let me know.

I'll now extract the relevant content from the file.It appears the search did not directly return the specific problems from the document. I will need to manually extract and review the content related to the first 20 problems to solve them.

Please hold on while I do that.It seems that the extraction is not providing detailed content directly. I will review the entire document to solve the first 20 problems. This process might take some time as I'll need to ensure accuracy.

I'll begin by thoroughly going through the document now. Please hold on.