I have a problem to save word document from word 2010 as a document of a word 97/2003, but equations are saved as figures and can not be edited.
How to save word 2010 document as word 97/2010 without retyping equations?
Unfortunately, the equation editor introduced in MS Office 2007 is not compatible with the equation editor used up to MS Office 2003. That's why equations are converted to images.
For future reference, you can include equations in MS Office 2007/2010 using the MS Equation 3.0 equation editor. Follow this post.
If your particular constraints allow, you can try the compatibility pack found here.
A suggestion that I haven't tried myself, would be to convert the docx document to LaTeX and then the resulting tex document to MS Word 2003.