Pick a random C from R. A and B have equal probabilities of being higher or lower than C. Now with the restriction A>B, there are only three equally likely opti

Pick a random C from R. A and B have equal probabilities of being higher or lower than C. Now with the restriction A>B, there are only three equally likely options: A>B>C, A>C>B, C>A>B. You can guess half the time correctly for A>B>C and C>A>B and all the time for A>C>B, which gives you 66% which is shown with the random trials.