Answer: 8 days
Explanation:
1) Set up an equation. Let x be the day
3,500 >= 2(816) + x(100+95)
The 816 is just two times (Plane ticket back and forth) so it doesn't go into the x. 100 and 95 do as it is one day.
2) Solve the equation
3,500 >= 2(816) + x(100+95)
1868 >= 195x
9.57 >= x
3) Rounding
Since the x has to be less than 9.57, our next option is 8