When you have three research problems is it better to write each of the problem with it's solution in same paragraph or write all the problems then the last paragraph should contain the summary of the solution?
When writing the findings of your research, it is important to have each research problem handled separately. For postgraduate students, in some Universities it is advised that you have a chapter for the findings for each research problem. In other universities you only have one chapter for findings but systematically provide findings for each research problem. Generally, every research problem should be handled separately Abubakar Isah
One of the secrets of academic writing is for each paragraph to answer a question that is in the mind of the reader but without stating what the question is. So, yes, do not answer more than one main question per paragraph.
Either ways are good! However, writing each of the problem with it's solution in the same paragraph would be easier for the readers to follow and understand.