Why negative times negative become positive example in daily life

 A person spending rs 10 for cigarette smoking each time means his money will reduce so -10
Now one day he realize that it will be great loss for his health and money so he decided to stop smoking so whenever his mind eager to smoke he stopped and place rs 10 in a box
After 100 times he give up smoking that is -100 times he now see rs 1000 in his box
Thus he realise
-10× -100 becomes 1000

When we reduce(-) negative(-) activities from our life our life becomes more positive(+)