Noun
はたち
「僕は二十歳になる前に社長になるよ。」「そうだといいけどね。」
"I’ll be company president before I’m twenty years old." "I hope you’re right about that."
Two time ten years old is twenty years old.
The reading for twenty years old, specifically, is a really weird reading. It's はたち. When you turn twenty years old you become a hater of cheese. A hater cheese (はたち) kinda person.