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<b>set </b><font color="Maroon">x</font> = 5 <a href="nat_1.html#K1">+</a> <font color="Maroon">n</font>;<br/>
<a NAME="E1:4_1_1"/>
5 <a href="xxreal_0.html#R1">&lt;=</a> 5 <a href="nat_1.html#K1">+</a> <font color="Maroon">n</font>
 
<b>by </b><i><a class="ref" href="nat_1.html#T29">NAT_1:29</a></i>;<br/>
<a NAME="E2:4_1_1"/><b>then </b>
5 <a href="nat_1.html#K1">+</a> <font color="Maroon">n</font> <a href="hidden.html#R2">in</a> <span class="p1">{<span class="default"> <font color="Olive">k</font> where <font color="Olive">k</font> is    <a href="subset_1.html#M1">Element</a> of  <a href="numbers.html#K5">NAT</a>  : 5 <a href="xxreal_0.html#R1">&lt;=</a> <font color="Olive">k</font> </span>}</span> 
 
;<br/>
<b>hence </b><a NAME="E3:4_1_1"/>
5 <a href="nat_1.html#K1">+</a> <font color="Maroon">n</font> is   <a href="zf_lang.html#NM1">Variable</a>
 ;<br/>


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