Sally and Wally

Sally goes to Wallys house during vacations. They play a chess game everyday and the loser has to give a chocolate to the winner for every game. Sally gave 8 chocolates at the end of the vacations, although she had won 12 games. How long did she stay there?

A Fly In Between Trains Problem

Two trains are traveling toward each other on the same track, each at 60 miles per hour. When they are exactly 120 miles apart, a fly takes off from the front of one of the trains, flying toward the other train at a constant rate of 100 miles per hour. When the fly reaches the other train, it instantly changes directions and starts flying toward the other train, still at 100 miles per hour. It keeps doing this back and forth until the trains finally collide.

If you add up all the distances back and forth that the fly has travelled, how much total distance has the fly travelled when the trains finally collide?

A boy at the Carnival

A boy was at a carnival and went to a booth where a man said to
the boy, "If I write your exact weight on this piece of paper
then you have to give me $50, but if I cannot, I will pay you $50."

The boy looked around and saw no scale so he agrees, thinking no
matter what the carny writes he'll just say he weighs more or less.
In the end the boy ended up paying the man $50.

How did the man win the bet?