HasSS}\#({Mary},n).$$<br />

3.  Everyone’s social security number has nine digits.<br />
    $${\forall\,x,n\;\;} {Person}(x) {\:\;{\Rightarrow}\:\;}[{HasSS}\#(x,n) \land {Digits}(n,9)].$$<br />

4.  Rewrite each of the above (uncorrected) sentences using a function
    symbol ${SS}\#$ instead of the predicate ${HasSS}\#$.
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        <a href="ex_28/" class="p-2">Exercise 28 </a>
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