"How much salt do babies and children need?"
Translation:Quanto sal bebês e crianças precisam?
No, it is not. But we have to get used to writing as close as possible to duolingo' sentence in order to not lose a heart...
In Portuguese we don't change the word's position to form an interrogative, we just change the intonation, so it's better say "Quanto sal os bebês e as crianças precisam?". Anyway it's not fully incorrect. It's clearly understandable.
Lingo, it is wrong: the verb precisar needs the preposition 'de': De quanto sal precisam os bebês e as crianças?