He is studying the shape of a decahedron.

My grandfather is seventy years old.

My grandfather is ninety years old.

My grandfather is already eighty years old.

When I was in my teens, I used to play soccer every day.

My father is forty years old.

My grandfather is already sixty years old.

My grandfather is already sixty years old.

My grandfather is already sixty years old.

He has been living in this town for several decades.