The problem
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Your software will not provide a solution for t
an error message appeared saying "_" is not a valid character. But I did not use that character. I have tried several times but the same message appears. so far this is not looking good after I have paid a years subscription.
Answer provided by our tutors
I have traced the problem to using subscripted variable button on the virtual keyboard and notified the development team. For the time being, simply type "u0" on the regular keyboard and 0 will turn into a subscript. This is the actual link to the solution:
and the solution:
