"Her steak does not have salt."
Translation:La sua bistecca non ha sale.
If this sentence has a word that is taught in the places topic, it could pop up. If in the places there is "Restaurant", probably they teach "Steak" as well (maybe in a sentence like "I got a nice steak at that restaurant"... hence steak would become a word of the lesson, and they could pick other occurrences of the word from other sentences in other lessons... at least, that's how I think it works).
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Lui does not mean her...and I don't think that's idiomatic...I don't know though
You are right I put lui instead lei, but it doesn't matter because when we write La sua bistecca non ha sale, we also don't know what do we have inside her or him.
"La sua bistecca non è salata" means "Her steak is not salty." "La sua bistecca è senza sale" is "Her steak is without salt." Neither are the translation Duo wanted. "Does not have" and "Is without" do pretty much mean the same thing, but since both work in English, we should use the one Duo asked for: "does not have," "non ha."
in Italian is better to say: "La sua bistecca non è salata" or "La sua bistecca è senza sale" not "La sua bistecca non ha sale".