it is easier to find the arrangement where every husband does sit next to his wife. to do this, we can consider each couple as one object with a permutation of 2! (since the wife can sit on the right or left of the husband). Thus we have 3 objects, each with a permutation of 2!. thus the number of seating arrangements where each husband sits next to his wife is 2!3!
so what is the probability of each husband sitting next to his wife? Hence, what is the probability that no husband sits next to his wife?