All the numbers together add up to $1+2+3+...+12=78$. There are six
couples, each with the same total amount, so this must be
$78/6=13$. So each couple's numbers add up to $13$.
I'm going to write the pairs in brackets, like this ( , ). The
first number is the one for the man, and the second for the woman.
So we know we have $(12, 1)$ and $(6, 7)$. We want the ladies'
numbers and the men's numbers each to add up to $78/2=39$. Here's a
way we could do it: