adjectives location question
At the beginning that I learned the adjectives should put after a noun. e.g. a white dog = un perro blanco.
A answer shows "una gran persona" is the correct answer and it does not accept "una persona gran".
Why do we sometimes put adjectives after a noun and sometimes put adjectives before a noun?
Are there rules when I need to put the adjectives before a noun vs after a noun?
In most cases, the adjective does go after the noun in Spanish. However, there are a few exceptions as you've discovered. There can be differences in meaning depending on the placement of the adjective.
Una gran persona = a great person (you drop the d or de only when it's placed before the noun)
Una persona grande = a big person