Question 1209090
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This is one way to do the derivation.
I'm using an ampersand (&) in place of a dot.
<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>~S</td><td></td><td></td></tr><tr><td>:.</td><td>~(F & S)</td><td></td><td></td></tr><tr><td>2</td><td>~S v ~F</td><td>1</td><td>Addition</td></tr><tr><td>3</td><td>~F v ~S</td><td>2</td><td>Commutation</td></tr><tr><td>4</td><td>~(F & S)</td><td>3</td><td>De Morgan's Law</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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