Question 1208734
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Here is one way to do the derivation. There may be other approaches.
<table border = "1" cellpadding = "5"><tr><td>Number</td><td>Statement</td><td>Line(s) Used</td><td>Reason</td></tr><tr><td>1</td><td>~D</td><td></td><td></td></tr><tr><td>2</td><td>B ⊃ (C ⊃ D)</td><td></td><td></td></tr><tr><td>:.</td><td>~(B • C)</td><td></td><td></td></tr><tr><td>3</td><td>(B • C) ⊃ D</td><td>2</td><td>Exportation</td></tr><tr><td>4</td><td>~(B • C)</td><td>3,1</td><td>Modus Tollens</td></tr></table>
Here's a list of <a href="https://www.algebra.com/algebra/homework/Conjunction/logic-rules-of-inference-and-replacement.lesson">rules of inference and replacement</a>
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