"They have good principles."
Translation:Ellos tienen buenos principios.
I got so frustrated with this one that I ended up spending about half an hour reading different sources on the topic of adjective placement. It sounds like either way is acceptable in this case. This seems to be a decent reference:
All in all, it sounds like some adjectives commonly come before the noun; if so, they're more figurative. Adjectives after the noun are apparently more literal.
I'll try to remember this by thinking about the "principles" being inherently good (adjective goes before the noun) rather than the principles being subjectively acceptable to the speaker (adjective after the noun). Maybe? This comes, as my Latin teacher once would have said, "ex recto."