Math expressions created in older InDesign version are garbled in CS6

[daisysdad]

I inherited ID files created in some version older than CS6. These are pages from a math textbook. When I open the files in CS6, the square root expressions, apparently written in the UniMath font, are garbled and can't be edited. They do not render correctly.

I'm running CS6 InDesign v.8 on a Mac running OS 10.11.6.

I'd be grateful if anyone can offer advice on how to fix this.

[BobLevine]

Are you sure they’re not linked/embedded EPS files?