Solution: The total number of ways to choose 3 distinct letters is $inom{26}{3}$. The favorable cases involve selecting 3 letters that correspond to exactly one placeholder symbol. Assuming each symbol is defined by a unique combination of 3 letters (with no overlap in symbol definitions), there are 10 favorable combinations. Thus, the probability is $rac{10}{inom{26}{3}} = rac{10}{2600} = rac{1}{260}$. $oxed{\dfrac{1}{260}}$

Thu, 30 Apr 2026 19:21:32 +0000

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