There are 12 persons in a dinner party, they are to be arranged on two sides of a rectangular table. Supposing that the master and the mistress of the house have are always facing each other, and there are two specific guest who must always, be placed alongside one another. Find the number of ways in which the company can be placed.
Number of ways master and the mistress of the house can be seated is $2 \cdot$$ 5 \choose 1$$=10$
Now, one position on every side is now fixed, Let us consider two specific guests as one element with two internal arrangements. For any side, we have to choose one position out of 3 but due to internal arrangements and two sides their arrangement becomes $2\cdot 2\cdot 3=24$
For remaining 8 persons the number of arrangements is $8!$.
Total Possible Arrangements = $10 \cdot 24 \cdot 8!$.
I now understand the problem in the following way: There is a table with dimensions $6\times 1$ in which for some reason people don't sit on the short edge. We wan't to count the number of ways to seat them so that the hosts are sitting in front of each other and the members of the couple are seated next to each other. We seperate in three cases:
Case 1: the couple hosts sit at the spots at the corner. There are two ways to select the side of the rectange and there are two ways to select which host sits at which of the two seats. After this notice the couple must sit at consecutive seats, how many pairs of consecutive seats are there? four on each side of the table, so eight. After this we must select which member of the couple sits in which of the two spots in two ways, and finally seat everyone else in $8!$ ways, so the answer is $2\cdot2\cdot8\cdot2\cdot8!$
Case 2: the hots sit at spots that are neither at the middle of the table or at the edges, there are $2$ ways to select the pair of spots they want, after this $2$ ways to select which couple takes which of the two seats. We now sit the couple, there will be three pairs of consecutive seats on each edge so there are $6$ ways to chose the pairs, $2$ ways to select which member of the couple takes which seat and $8!$ ways to sit everyone else. The answer is thus $2\cdot2\cdot6\cdot2\cdot8!$
Case 3: the hosts sit at central spots,there are two ways to select which of the central spots, then there are two ways to select which host gets which of the two spots, notice there are three pairs of consecutive spots left on each side, so there are $6$ ways to select the spots the couple sits at, and then $2$ ways to select which member of the couple gets which seat, after this $8!$ ways to sit everyone else, hence there are $2\cdot2\cdot6\cdot2\cdot8!$
factoring the $8!$ the final answer is:
$(64+48+48)8!=160(8!)$