Its 16.
So you have 12 miles on that trail, and markers every 2/3 of the way there. If you were to divide 2 with 3 then you can get the decimal of the fraction. Which in this case it’s 0.75. So every single 0.75 of the mile there is a marker. Divide 12 with 0.75 and you get 16 markers.
Hoped this helped in some way.
