17/35
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To find the probability that only one of two people will win a race, given their individual probabilities, we need to use the following logic:
The probability of Person A winning is 2/5, and thus the probability of Person A not winning is 1 - 2/5 = 3/5.
Similarly, the probability of Person B winning is 3/7, and the probability of Person B not winning is 1 - 3/7 = 4/7.
We calculate the probability of each scenario separately:
Now, we add the probabilities of these two mutually exclusive events to find the overall probability that only one will win:
Therefore, the probability that only one of them will win the race is 17/35.