This problem falls into the category of mathematics.

This brass vase is very beautiful.

It's difficult to understand what's in his heart.

This road is under construction, so you cannot pass through.

He is receiving treatment for alcoholism.

My computer is currently under examination.

This book is an annotated edition of his work.

Rikuchū is a former place name in Japan, referring to a part of present-day Iwate Prefecture.

He is working hard on his Japanese studies day by day.