! is factorial it means multipliy all numbers from 1 to that number together example 1!=1 2!=2*1 3!=3*2*1 etc
some things to note 7!*8=8! 4!*5*6=6!
[tex]\frac{(4!)(7!)}{(6!)(8!)}[/tex] so we can rewrite it as [tex]\frac{(4!)(7!)}{(4!)(5)(6)(7!)(8)}[/tex]= [tex]\frac{1}{(5)(6)(8)}[/tex]= [tex]\frac{1}{240}[/tex]
