Definition:
Springfield => S ,Fort Wayne => F , Toledo => T, Indianapolis =>I
A<>B means distance between A and B.
A<>B = B<>A

A. Springfield, Fort Wayne, and Toledo lie on a line.
S<>F is 254 , F<>T is 89 , and S<>T is 343 = 254 + 89
If S,F,T does not lie on a line, S<>T should be smaller than 343.
True :

B. Indianapolis is the midpoint of the line segment connecting Toledo and Springfield.
False:
If Indianapolis is the mid point of the line segment T<>S, T<>S = T<>I + I<>S
343 ,T<>S is not equal to 183, T<>I, + 186, I<>S, so Indianapolis is not the mid point of line segment connecting Toledo and Springfield

C. Indianapolis, Toledo, and Fort Wayne are the vertices of an equilateral triangle.
False
Every side of an equilateral triangle should have same length.
I<>T, T<>F, F<>I should have same length in case these cities are the vertices of an equilateral triangle.

I<>T : 183
T<>F : 89
F<>I : 101
Obviously their values are not equal.