Hi,
I tested in 2.06. I think it will work in your version. EM was introduced in version 1.92.
What is a "student licence"? Is it an university installation? There might be some right restrictions.
To answer your question:
What kind of equation I need to put in?
Well, you have to check, that either the number of answers is 6 (and the "Other" is empty) or the number of answers is 7.
Set the question to "not mandatory" and the question validation to:
(count(self)==6 and count(self.sq_SQ007)==0) or count(self)==7
And add a appealing tip; so it is fine.
On the other side I never know why people want to have an "Other"-option in a matrix.
In my opinion respondents usually do not select "Others" and rate it "seldom" or "never".
So you get a bias and means are not comparable.
And furthermore you do not know, which "Others".
What is the meaning of "54% look for other informations daily"
Therefore I prefer a following open question like "Are there other informations ... which you look for ... frequently?"
So after the pretest you might get some "other informations" which are worth to be included as a precode in the matrix.