"That is a good idea!"
Translation:¡Esa es una buena idea!
Eso es una buena idea is given as another correct answer. Could someone please explain why that is correct. Gracias.
I believe it should accept "es una buena idea" that's at least what all my Mexican friends say.
Buena/Bueno is one of those adjectives that can precede the noun as well as follow it. Not sure why your version is not accepted. Maybe there is a rule here specific to this sentence I don't know. If you precede the noun in masculine form, remember to drop the o from bueno, making it buen. I was using that a lot any time I was watching Robben from the Netherlands during the Copa Mundial 2014 - I would fin myself shouting "Buen Actor!, Buen Actor!" every time he took a dive, trying to draw an infraction. I am pretty sure there is a price out on his head in Mexico.