I just found out what the problem is.  I had set my documents globally to 150% (I am 79 years old and my eyesight is not what it once was). When I changed globally the setting back to 100% I was able to resize the imported image. 

@Samir Khan Thank you for the help.

Julio Santander

@Samir Khan  Will do.

I tried that and did not work in the file I was working on. Then, I open a new document and put the same values I had before, and I was able to use the context panel. I wentn back to the original file, and I could not change the units. There must be a glitch in that file. Like I said, when I started a completely new document I was able to use the context panel to change the units.????

Thanks.

Thank you for the help. It worked.

I forgot to mention when I posted the question that I was working in the "Document" format. I have not tried the "Maple" or "Woksheet" format. I will do so tomorrow and see what happens. Thank you to Carl Love 7800 for posting an answer to my question.