Answer
$C(11,1)*C(10,2)*C(8,4)*C(4,4)$
Work Step by Step
We have to find the total number of sequences that can be formed using the letters of the word Mississippi.
It has 11 letters. (1m,2p,4s,4i)
The total number of 11-letter sequences of those letters is $C(11,1)*C(10,2)*C(8,4)*C(4,4)$
Because first we choose where to put the m in the sequence, then the two p's, (we can't put them where the m is), then the 4 s's, and the 4 i's.