"Twelve-year-old" is the correct way to write the age of a twelve-year-old individual. The phrase should be hyphenated when used as an adjective before a noun.
twelve because if they are twelve they are twelve.
"She has behaved like a twelve-year-old for the last twenty years."
Babysitting is the best job for a twelve year old
disapline
Yes it is appropriate for a twelve year old.Yes it is appropriate for a twelve year old.
how can yu make algebra equations easy for a twelve year old
Yes, you have the ability. No, no one will appreciate a twelve-year-old humping them. Except, maybe, another twelve-year-old.
twenty twelve
Yes, a twelve year old can move in with the other parent.
The correct way to write the year on an invitation is "two thousand twelve." This follows the standard format for writing out the year in words.
Yes
In the fictional Crucible, Miller does not describe that. In reality, no one cared enough about a twelve year old who was important for a year and then vanished to write about her personality.