At a party people shake hands with all the people they do not know. A married couple organizes the party; they only invite other married couples. It is assumed everybody knows him/herself and his/her partner.
When all couples have arrived and all the handshaking has been done, the host mingles among the guests and asks everybody (including his wife): "How many hands did you shake?". To his surprise, all responses are different.
With the above information, you should be able to determine how many hands the host and hostess each shook.