Answer: 171 attendees
Explanation:
I answered another similar question by you earlier, so I really hope you read through this explanation, as I will go far in depth. It's important you learn to do this so as not to simply skate through homework, then struggle with assessment.
For this problem, you have to find something called a unit price.
A unit price is the price in dollars per thing.
In this case, the price in dollars for the whole group is $132 for many things, 66 attendees.
Because 66 attendees costs $132, to find out how much money a single attendee costs, simply divide $132 by 66 to get 2$ for 1 attendee.
With this information, it is very straightforward to determine the number of attendees for $342. Simply divide $342 by $2 to get 171 attendees.
I really hope it helps :) and please, let me know if you want me to explain in more depth, the unit you are currently in is a fundamental part of early math, and it is important you understand it.