How Many Triangles Are There?

A couple is dressed and ready to go out for the evening. They phone for a cab, turn on a night light, cover their pet parakeet and put the cat out in the back yard.
The taxi arrives, and they open the front door to leave. Suddenly the cat they put out scoots back into the house. They don't want the cat shut in there because she always tries to eat the bird. The wife goes out to the taxi while the husband goes back in. The cat runs upstairs, with the man in hot pursuit.
The wife doesn't want the driver to know the house will be empty. She explains to the taxi driver that her husband will be out soon. "He's just going upstairs to say goodbye to my mother."
A few minutes later the husband gets into the cab.
"Sorry I took so long," he says, as they drive away. "Stupid hag was hiding under the bed. Had to poke her with a coat hanger to get her to come out! Then I had to wrap her in a blanket to keep her from scratching me. But it worked. I hauled her fat butt downstairs and threw her out into the back yard!
The cab driver hit a parked car.