Can Sass perform mixed arithmetics?

I am in a bit of a dilemma here... According to this stack overflow question's accepted answer, Sass cannot process expressions involving px and % together. However, if I go to the Sass Guide and scroll down to the Operators section, there is a very clearly written expression involving px and % together. Is this a mistake in the Sass documentation, or does this expression really work?

I know the only way to know for sure is to try it out, but since my laptop is fried and I am writing from my phone, there is no possible way I can check it within this week... So, I posted this question.

Hope somebody satisfies my curiosity :P

Thank You