300
A group of criminals decided to run away before the police catches them, and they all had to pay some money for the plane ticket. Four of them were arrested on their way, and the rest of them each had to pay extra $200 for their tickets, and it costs $3000 in total. How many criminals were their in the beginning?
(3000/x-4)-(3000/x)=200
3000x-3000(x-4)=200x(x-4)
3000x-3000x+12000=200x(x-4)
12000=200x^2-800x
200x^2-800x-12000=0
x^2-4x-60
(x+6)(x-10)=0
x1=-6 (rejected)
x2=10 (check)