I think the only confusing part of it is the sentence<p>&gt; The number of phones that she has left to fix at the end of each day can be estimated with the equation<p>&quot;Has left to fix&quot; could be misinterpreted as meaning &quot;she has to fix this many,&quot; instead of simply &quot;how many remain.&quot;<p>If you understand that it&#x27;s just saying &quot;P is how many remain&quot;, then it&#x27;s clear that the formula is simply saying that she started with 108, and she fixes 23 per day.