Answer: The first option, 52 ft.
Explanation:
The data we have is: 
The diameter of the lawn is 100ft. 
Between the two pats, we have a 60° angle, so we want to calculate the distance between both paths, walking around the circle, this would be the length of the arc of 60°. 
Now, first, we know that the perimeter of the circle is equal to 2*pi*radius. 
So a section of the perimeter can be calculated as: 
L = Angle*radius. 
But we need to write the angle in radians. 
We know that 180° = pi = 3.14 
then (60°/180°)*3.14 = 1.04 
60° is equivalent to 1.04 radians. 
Now, we have the diameter of our circle, and we know that the radius is equal to half the diameter, so if d = 100ft, r = 100ft/2 = 50ft. 
Then the length of the arc is: 
L = 1.04*50ft = 52.3 ft 
Then the correct answer is the first one (where the result is rounded to the next whole number, 52 ft.)