The Fibonacci Sequence is a stream of numbers that typically begins with a "0" or "1". From there, any number placed after would be added to the previous number.
For instance, if I started with a "1", and the next number was a "2", the number after would be a "3". From this "3", it would be a "5", the next number would then be a "8".
It would look like this:
1, 2, 3, 5, 8
Let x represent the number originally signed up.
.. 360/x -6 = 360/(x +3)
.. 360*(x +3) -6x(x +3) = 360x . . . . . multiply by the product of denominators
.. 360x +1080 -6x^2 -18x = 360x
.. x^2 +3x -180 = 0
.. (x +15)(x -12) = 0
Solutions are x = {-15, 12}
12 members went on the trip.
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The problem wording does not make clear whether the original number (12) or the number suggested by the bus company (15) went on the trip. It would be most reasonable for 15 to go, if the troop had people who were willing.