I'm going through old papers I found on the internet and found this question which has perplexed me, any help would be appreciated.
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Propositional Logic and Set Theory Question
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logic
propositional-calculus
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0$(D)$ is equivalent to $x=7$ – 2017-01-12
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1Answer is D.... – 2017-01-12
1 Answers
1
As commented before, $$7\in \{6,x\}\Rightarrow 7=6\;\vee\;7=x\underbrace{\Rightarrow}_{6\ne 7}7=x,$$ and now, we can conclude.