"They are not good."
Translation:Eles não são bons.
you have to write bons.
Not with elas which is the feminine form of they so requires the declension of good to boas (for feminine and plural agreement).
Since we have no context on whether they are male or female (or masculine/feminine it), then Duo needs to accept both forms translated into PT (and probably does by now, 4 years later :D).
But, the real issue above is that nao needs to come before the verb it negates. So, elas não são boas instead of, elas são não boas.
Bons estudos! :)
Estão for the verb Estar is a different form of "to be" for Portuguese that alters the meaning a little bit.
The verb Ser is used for conditions or characteristics that are permanent and the verb Estar is used for transitory or impermanent conditions or characteristics.
Nuno é um homem (Nuno is a man) – he just is... he won't wake up tomorrow as a woman (barring some major intervention). :) Or, Nuno é português (Nuno is Portuguese), which he still will be even if he moves to another country.
Nuno está com fome (Nuno is hungry) – In this moment Nuno is hungry, but hopefully not all the time or forever.
Some other examples of transitory conditions or characteristics include being sick, tired, angry, cranky, at the store, curious, warm, cold, dry, wet, raining, sunny, walking, running, driving, stuck in traffic, showering, talking, writing, reading...
So "estão implies they are temporarily not good, but because "they" (eles/as) is a plural it does indeed require the rest of the sentence to follow the plural so "bons" not the singular of bom.
Also, if it were "Elas" (or some other feminine for example, as gatas, as meninas) then "bom" would be declined to "boas" for the plural feminine.
Bom Fim de Semana (Good End of Week)
Boa Semana (Good Week).
Just to make it a bit more complicated, the singular object adverb form for "bom" (normally an adjective) is "bem" as in "Ele está bem" for "He is well." In English this could be illustrated by, "He did a good job" versus "He did well on his job." or in this sentence, They are good" (perhaps a music band) versus, "They are well" (no one in the band is sick).
Subtle, but it comes. We were not born knowing any languages.
Hi Philip, bom is singular. The answer you gave is plural and masculin "eles estao" so you need to stick to it and use the plural masculin form of "bom" which is "bons". Took me a while to get my head around ;). Many words change according to the gender and number of the noun they refer too.
2019-11-18 It doesn't look like anyone has corrected the assertion that "They are not good" is singular. It is not. Generally, English adjectives are invariant. That is, "good" does not become "goods" for plural nouns or pronouns. The use of the plural pronoun "they" and plural conjugation "are" indicates that the sentence is plural.
Sure, with enough context we can drop the pronouns even in the Brazilian form of Portuguese (and it's possible too in English... with enough context).
But as I keep saying, if there is anything lacking on Duo it is context. So we have to provide it, and the way to do it here (where pronouns share a conjugation) is to include the pronoun so it is not ambiguous. :)