There are 6 married couples at a party. At the start of the party, every person shakes hands once with every other person except his or her spouse. How many handshakes are there?
Note that the first couple each shake 10 hands
The next couple each shake 8 hands
The next each shake shake 6 hands....etc.
So 2 * (10 + 8 + 6 + 4 + 2) = 60 handshakes