I explained many times to make him understand the math problem.

That problem is difficult, I don't understand.

I don't know if he will lend me a thousand yen.

He hung a hook on the wall.

Takagi is my best friend.

Vermiculite, in mineralogy, is a type of mineral and is used for various purposes due to its characteristics.

The grammar of 'Jou-nidan' is an important part in learning Japanese.

My room is on the upper level.

The population of this town is rapidly increasing.

There are a hundred houses in this town.