This error is due to a communication breakdown between the user's browser and MathJax, a third-party program that helps us display fractions and other math symbols. MathJax isn't native to most browsers, so it's possible for a page in the course to load before all the communication between MathJax and the browser wraps up, resulting in the [Math Processing Error] wherever math symbols should be. This is all context, though, and nothing the user needs to understand to fix the problem.
You'll hardly ever see these errors in Firefox. This makes switching to Firefox the easiest and fastest fix to this problem. However, we're creatures of habit, so if this isn't a viable solution, tell the user to follow these steps:
1. Right-click on the error message.
2. Select "Math Settings" from the drop-down list.
3. Select "Math Renderer" from the secondary drop-down list.
4. Select one of the renderer options not currently in use. "SVG" is consistently legible, but possibly slower than other renderers.
5. If this does not solve the issue, try a hard refresh, which is executed by holding your Shift key and then clicking the Refresh/Reload/whatever button in the browser you're using.
6. If the hard refresh does not solve the issue, clear your cache and restart your browser.