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here We have to find out the arrangements among 8 people if there are no restrictions on the seating arrangement

if there no restrictions then the permutation will be$8!=40320$

We have to find the seating arrangements among 8 people if persons A and B must sit next to each other

If A and B sit next to each other they will form a group, then there are 7 objects and the arrangement between A and B is 2!. Thus the seating arrangement will be$7!脳2!=10080$

We have to find the seating arrangements among 8 people if there are 4 men and 4 women and no 2 men or 2 women can sit next to each other

If 4 men and 4 women each are in a group, then there will form 2 groups and the permutation of this group is 2! and within a group of men and women arrangement will be $4!脳4!$. Thus if there are 4 men and 4 women and no 2 men or 2 women can sit next to each other , then the arrangement will be$4!脳4!脳2!=1152$

here We have to find out the arrangements among 8 people if there are 5 men and they must sit next to one another

if 5 men and they must sit next to one another then this will form a group and arrangements within the group will be 5!.So there will be one men group and 3 women. thus the permutation will be$5!脳4!=2880$

We have to find out the arrangements among 8 people if there are 4 married couples and each couple must sit together

If there are 4 married couples and each couple must sit together, there will form 4 pairs of couples and the permutation will be 4! The arrangements within each couple is 2! and so permutation of the given question will be$4!脳2!脳2!脳2!脳2!=384$