--FURTHER INSTRUCTIVE COMMENTARY---
The proof or at least logical demonstration should be found in your book. You can start this way:
You already understand that , basic fact, easily demonstrated with repeated additions.
You may already understand, -6*2 means the same as 2*(-6), which is
and since you can refer to a numberline using signed numbers, you will find .
Now you want to take the next step and understand how , the positive number. Try THIS:
but theoretically this still is not a proof for you. What it shows is THE OPPOSITE OF NEGATIVE 12. , the positive quantity.
This can not be made much easier.
Do not be thrown off by the need to read the notation.
-6*2 means exactly the same as (-1)*6*2, which is or should obviously be .
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