She will soon be a twenty year old student. Her boyfriend has an old car. He has a twenty year old car. He is a 22 year old student. He has a ten-year old sister.
Adjectives can sometimes change their meanings according to the preposition they are followed by.
Internet Help Adjectives defined , from Illinois University. Adjectives with countable and uncountable nouns , from Purdue University. An Interactive Book is meant for a diverse audience, in public schools, private schools, colleges, universities, and businesses.