Question 1111681
The 13 tosses can be thought of as 13 places to hold results.  In one case we want to distribute two identical items in those 13 places (13C2) and in the other, 9 identical items are distributed amongst the 13 spaces (13C9).  

Then we add them because they are two distinct scenarios:

 {{{ 13C2 + 13C9  = 78 + 715 = highlight(matrix(1,3, " " , 793, " " ) ) }}} 

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Dear student,

{{{ nCr = n!/((n-r)!r!) }}}

{{{ 13C2 = 13!/((11!)(2!)) =  13*12/2 = 78 }}}     <<< the 11! cancels all but 13*12 in the numerator

{{{ 13C9 = 13!/((4!)(9!)) = 715 }}}   <<< here,  9! cancels most of the numerator

Hope this clears it up!