I found the answer on another thread, of which I will just paste part of it: "The first has mixed declension due to the 'keine'. For plurals (in all cases), this is -en. The second has strong declension, due to the lack of any article. For plurals (in nominative/accusative), this is -e. I can't recommend enough bookmarking this page: http://en.wikipedia.org/wiki/German_declension#Attributive_adjectives. Learning from the tables may not be the easiest method to understand German adjective declension (check out http://www.youtube.com/watch?v=r6VeAWFZs_c), but it is VERY handy just to double check if you aren't sure, especially if you are trying to get through the lesson on that last heart!"
The rule is actually really intuitive - German needs the noun modifier to convey the gender and case, so if there already is something like 'ein' 'das' 'kein' 'sein' , then the adjectives all just take the regular endings, but in the absence of those modifiers, we need to know more info about the noun, so we add the appropriate endings to the adjectives.
Ich mag das große Haus Ich mag ein großes Haus (we use großes because ein could be masculine or neuter so the es at the end of großes clarifies that it is neuter)
I'm wondering the same. I think your translation is actually closer to the german text given here. I'm still very confused by the use of nicht and kein. I would guess that "Sie mag keine modernen Häuser." is "She doesn't like any modern houses?" while "Sie mag modernen Häuser nicht." is "She does not like modern houses." Could anyone shed some light?