Stay in China for the High School

I decided to stay in China for the High School years. Therefore, I have to take the test which is called Zhongkao in China. It is one of the most important tests that will be taken in my academic years.

In order to pass the test, I need to solve this problem.

At a party, everyone shook hands with everybody else. There were 66 handshakes. How many people were at the party?

1. 12
2. 30