How do you simplify $(21!)/(14!)$ ?

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Answer 1 · 2016-10-13T14:44:43

By cancelling common factors.

By definition:
$21! =21xx20xx19xx....xx15xx14xx13...xx2xx1$
$14! =14xx13xx12xx....xx2xx1$

So we can cancel all factors from $14$ downward.
Which leaves:

$=21xx20xx19xx18xx17xx16xx15$

How do you simplify (21!)/(14!)(21!)/(14!)?