That surprises me. Send a Word doc with an example via my site. Please include a link to this thread in your email.
See www.grainge.org for RoboHelp and Authoring tips
Having seen the Word file sent, I can see the problem. The equations are seen in Word as an object. That is an unknown in HTML so RH is converting it to an image.
I can't see a way of stopping that but there is an alternative workflow with RoboHelp 8. You don't say which version you are using so I don't know if that is an option. For future posts, please read Before You Post as it helps us give you a better answer quicker.
RH8 allows you to link to Word documents rather than importing them. You could therefore maintain those topics with equations in Word and have a link. That would allow you to create topics in RH. When you generate the help, you would allow RH to update the topics from the source Word document.
If you don't have or can't upgrade to that, I think you are stuck with the problem. Obviously check the trial before you upgrade to be certain it suits your needs.
See www.grainge.org for RoboHelp and Authoring tips