Hey, I've got this puzzle that I'm trying to work out. It seems simple, but I can't seem to form a coherent equation to build in order to solve the puzzle.

The puzzle is this.

A group of friends are going on a flight, and are going to split the costs between them, so that the total comes to 6000 dollars. At the last minute, 3 of the friends can't make it, and everyone else has to pitch in an additional 100 dollars each to cover the costs. How much are the price of the tickets per person?

Any help would be great. Thanks.