Idon't understand what the question is asking?

Check the picture below.

bear in mind that 100/10 is 10, however, we have to include the very first post, which is not spaced away 10' from anywhere, is simply touching the barn wall.  So the total is 10 spaced 10' from each other plus the starting post which is touching the barnwall.  And you can start doing the counting from either side A or B and you'd get 11 total.

Notice the angle "tickmarks" btw, that means those two angles are equal, that means the triangle is an isosceles, and thus both of those sides are equal, so, if one is 50', the other is also 50'.

Definitely