The number of people attending the meeting was n, so everyone shook hands (n- 1) times.

Therefore, n(n- 1)/2=66.

n(n- 1)= 132

n= 12

Therefore, the number of participants this time is 12.

Let's line up the people attending the meeting, get off the queue from the first person and shake hands with the people behind, so that every two people attending the meeting can shake hands once ~

So it can be assumed that the first person shakes hands n times, and the latter shakes hands n- 1, n-2, n-3 ... times in turn.

1+2+3+4 ...+n = 66. The solution is n= 1 1.

That is to say, the first person shakes hands 1 1 time, then a *** 12 person attended the meeting.