Please tell me the way to solve this problem.

We are considering introducing a new voting system.

The police used a water cannon against the demonstrators.

Learning a new input method is difficult.

My four treasures of the study are a fountain pen, a pencil, an eraser, and a ruler.

He achieved the Nine Gates in mahjong.

He pulled the door open.

He flipped the pages of the book.

He won in Mahjong with the Yakuman hand of Suuankou Tanki Machi, and the number of Han was 13.

He is suffering from lovesickness.