I really don't want to seem rude, but I seem to recall you've asked variants on this exact question multiple times in the past. A quick review confirmed this recollection, as evidenced by
this thread from April 2015, this thread from June 2015, and
this thread from March 2017.
In each of those threads, you received an answer to your query, to indicate that the order of division
does not matter with these so-called "complex fractions." Here, too, we can see that's the case.
\(\displaystyle \dfrac{\dfrac{$6300}{35\:students}}{24\:days} = \dfrac{$6300}{35\:students} \cdot \dfrac{1}{24 \:days} = \dfrac{\dfrac{\dfrac{$6300}{35}}{24}}{\dfrac{student}{day}} = \dfrac{$7.50}{\dfrac{student}{day}}\)
\(\displaystyle \dfrac{\dfrac{$6300}{35\:days}}{35\:students} = \dfrac{$6300}{24\:days} \cdot \dfrac{1}{35 \:students} = \dfrac{\dfrac{\dfrac{$6300}{24}}{35}}{\dfrac{day}{student}} = \dfrac{$7.50}{\dfrac{day}{student}}\)
As you (should) know, "$7.50 per student per day" is exactly equivalent to "$7.50 per day per student."
More generally, for
any real A, B, and C of
any units, we can say the following:
\(\displaystyle \dfrac{\dfrac{A\:unit\:1}{B\:unit\:2}}{C\:unit\:3}=\dfrac{\dfrac{A\:unit\:1}{C\:unit\:3}}{B\:unit\:2}=\dfrac{\dfrac{\dfrac{A\:unit\:1}{B}}{C}}{\dfrac{unit\:2}{unit\:3}}\)
