Why does -3 - (-6) = 3

I don't understand. I know the rule is subtracting two negatives equal to adding but i don't get what's the logic behind that?
Can anyone explain please.

Think about subtracting negatives. If you are subtracting positives, obviously, you are going in the negative direction-- like going to the left on a number line. But if you are subtracting a negative, then you are actually going to the right on a number line because you are getting rid of negatives. Positive and negative are opposites, so you are just doing the opposite of losing, which would be gaining.

Its the same with language; a double negative make a positive.

Suppose you have a debt of three dollars and I owe you six dollars (that (-6) there); its six dollars you DO NOT have. Now I pay off my debt to you; you can pay off YOUR debt and have three dollars left over.

So :) can I now borrow three dollars please?

Whenever you have two negatives you get a posative so really this equation is -3+6=3
Ok here's another one -1-(-4)=3 you would take the two negative signs in the middle and make it a posetive (-1+4=3)

Hope this helps!

-3 - -6 = 3
you can read it like this too because 2 negatives equals a positive:

-3+6=3
-3 -2 -1 0 1 2 3 4 5 6