Try this test to see if your losing your marbles.
You are driving a bus carrying 17 people from London to Wales.
On the way people get on and off the bus. In Reading 7 people get off and 3 people get on, in Stratford 6 people get on and 7 get off. In Cardiff 10 people get off and 5 people get on and in Camarthen 5 people get off and 8 people get on.
What is the age of the driver?
Don't you know your own age?