My younger sister is twenty-one years old.

My room is on the upper level.

They are treating all students as one.

He tends to regard all people as the same.

Her dress was a single point of red, standing out in the party.

Solving a linear equation is difficult.

The first storm of spring blew fiercely, and the cherry blossom petals fluttered up.

I learned the meaning of 'ichi ni ten' in the classical Japanese class.

This is a once-in-a-lifetime opportunity.

He and his brother look so alike, they seem like the very same person.