"Yo voy a salir de casa muy pronto."
Translation:I am going to leave home very soon.
I don't think that "I am going to go out of the house very soon", is going to be right. I think that Duo did it just fine.
08/12/18. My answer ("I am going to leave from home very soon") was counted wrong. But think this should be an acceptable alternative answer. According to www.spanishdict.com, one of the definitions of "de casa" is "from home." To me as a native English speaker, both the DL English exemplar and my answer are common, natural, and grammatically correct ways of saying the same substantive thing. Have posted.
I wrote "I am going to leave home very early" - DL said, the correct version was "I am going to leave home very shortly."
I never heard "shortly" before.
"Pronto" (soon/shortly) and "temprano" (early) are not the same thing. Let's say I had to leave the house at 6:00. We would write that as "Tengo que salir de mi casa a las seis." If it's 5:45 and I'm still leaving at 6, I would be leaving soon, not early. However, if it's 5:45, and I decide to leave at 5:45 instead, I would be leaving early, not soon.