Hello, 

this is another validation issue which created frustration among the students: Both inputs x0 and x_0 are displayed the same in validation.  Once my teachers solution uses x0 any answer with x_0 is refused, athough the students are convinced they did it right.

Is there an option to ignore underscores in answers? 

A workaraound for me is to use an extra PRT entry with SAns=ev(ans, x_0=x0).

Now that I write this, it comes to my mind that I also probably could define x_0:x0 in the question variables, once I am aware of the problem. 

Yet I keep this post to ask for a generic recommendation to handle this.