Question: How to make maple execute/save the text written with the symbolic text?

Hello everyone, I have some weird problems with the maple. The problems are different for the document mode and the worksheet mode, however I strongly believe that they are connected. Starting with the document mode:

I simply cannot execute any command with the symbolic notation. As you can see below, I can execute basic mathematical calculations but I can't do any symbolic math. 

On the other hand, I can execute all the commands in the worksheet mode. For example check the screenshot. 
However, when I try to save that file in the worksheet mode, I get this error:

And, when I close the file and re-open again, I find all the stuff I wrote in the "math mode" disappeared 


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