While I was driving...

I was driving with my wife at my side and my mother-in-law in the backseat. They just wouldn't leave me alone.
My mother-in-law said, "You're driving too fast!"
My wife said, "Stay more to the left."
After ten mixed orders, I turned to my wife and asked, "Who's driving this car - you or your mother?" 

And that's when the fight started...