Solve the puzzle!

I borrowed from Billy of $ 100 went to the store and along the way they lost
Met Michael and took a loan from him of $ 50 , went to the store and bought chips for 20 $ the other 30 $ I gave Billy owed him $ 70 and $ 50 Michael .
I have 120 $ and I got the chips for $ 20 , where are the other 10 $ ???