Matthew and Christopher set up their Teenage Mutant Ninja Turtles in a big circle, spacing each turtle equal distance from its neighbors. They then begin counting them in order around the circle, but they lost track of where they started before they finish counting. They then notice that the sixth turtle is directly opposite the seventeenth turtle, and they realize that they can still figure out how many turtles are in the circle. How many turtles are in the circle?
Is the answer 21 I am not sure..