B.
The shortcut is the hypotenuse of the triangle, which is the straight line from Nene to Juan. To find its length, use Pythagorean theorem: [tex]a^2 + b^2 = c^2[/tex] , where C the hypotenuse, and A and B are the legs of the triangle.
[tex]c^2 = a^2 + b^2 c^2 = 13^2 + 8^2 c^2 = 233 c = \sqrt{233} = \boxed{15.26 m}[/tex]
C.
Distance without shortcut: 21 m
Distance with shortcut: 15.26 m
Distance saved: Without - with = 21 - 15.26 = 5.74m