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Simple solution:
Probability that Bob takes one of the ends: 2 out of 5 seats (2/5)
Probability that Lisa takes the other end: 1 out of the remaining 4 seats (1/4)
2/5 x 1/4 = 2/20 = 1/10
QED
Edit: BTW, as you can tell by the calculation, OP is misreading the question. In order to sit next to only one other person, Bob and Lisa must necessarily sit at the ends.
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