You can put this solution on YOUR website! I have 6 and you take away 6. I have 0.
If your bank account is at $6. You make a purchase of $6. Your bank sees this as -$6. Now your bank balance reads $0.
6 + -6 = 0.
You can put this solution on YOUR website! 6+(-6)=0
You would take the six and add negative six, which is like subtracting six from negative six.
Please comment back on how well you think I solved your problem. Thanks.