Perhaps the following site might be useful http://italian.engagedthinking.com/lessons/Lesson_194.pdf
I agree. When I first heard the trovare expression, I thought is was so odd. I have noticed other expressions on DUO that I was told were incorrect. You DO NOT love anything except your family or very serious boyfriend. Languages do change throughout various sections of a country. The fact that I studied in Toscana could be the difference. Non lo so. (my favorite expression) Also, I have heard that there is a "street Italian" whose words have filtered into the language. TU is used more readily now.
i translated this, just to be difficult, "the boy visits her grandmother," which as far as i know should also be correct, and lost a heart. of course the more obvious translation is that the boy visits his own grandmother, but couldn't it be someone else's grandmother also?
Generally with close family you do not use the definite article, so 'sua nonna' is the correct answer. Italian has a rather strict set of rules for these situations http://italian.about.com/library/fare/blfare124a.htm
Two reasons. First, you are using a different verb. "To pay" is not the same verb as "to visit". For any given statement in English there are usually other words that you can use to mean more or less the same thing. However Duo is asking people to translate the words that are there, not put the expression into other words. Second, you don't "pay visit" in English but rather pay a visit.